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REESE    LIBRARY 

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OF   THE 

UNIVERSITY   OF  CALIFORNIA 

Deceived  ^ 
Accessions  No.^,. Shelf  JVo. 


ELECTRO-CHEMICAL 
ANALYSIS. 


SMITH. 


RlCHTER'S 


AUTHORIZED  TRANSLATIONS. 


BY  EDGAR  F.  SMITH,  F.C.S.,  M.D.,  PH.D., 

Professor  of  Chemistry,  University  of  Pennsylvania  ;  Member  of  Chemical  Societies 
of  Berlin  and  Paris,  etc. 


INORGANIC   CHEMISTRY.     A  Text-book   for   Students.     Third 

American,  from  the  Fifth  German  Edition,  thoroughly  revised,  and 

in  many  parts  rewritten.     With  89  Illustrations  and  a  Colored  Plate 

of  Spectra.     I2mo.  Cloth,  $2.00 

THE    CHEMISTRY  OF   THE   CARBON    COMPOUNDS,  or 

Organic  Chemistry.     A  Text-book  for  Students.     Translated  from 
the  Fourth  German  Edition.     Illustrated. 

Cloth,  $3.00;  Leather,  $3.50 

Prof.  Richter's  methods  of  arrangement  and  teaching  have 
proved  their  superiority  by  the  large  sale  of  his  books  throughout 
Europe  and  America,  translations  having  been  made  in  Russia, 
Holland  and  Italy.  They  are  now  used  by  many  of  the  most 
prominent  schools  and  colleges  in  the  United  States,  by  those 
giving  a  high  technical  education,  as  well  as  those  who  aim  to 
give  but  a  groundwork  in  the  science  of  chemistry ;  this  shows 
their  wonderful  adaptiveness  to  all  grades  of  teaching. 

Upon  application,  a  complete  descriptive  circular,  giving  recom- 
mendations and  examination  prices,  will  be  sent  free. 

P.  BLAKISTON,  SON  &  CO., 

PUBLISHERS, 

1O12  WALNUT  STREET,  -'  PHILADELPHIA. 


ELECTRO-CHEMICAL 
ANALYSIS. 


BY 


EDGAR  F.  SMITH, 

M 

PROFESSOR    OF    ANALYTICAL    CHEMISTRY,    UNIVERSITY    OF    PENNSYLVANIA. 


WITH  TWENTY-FIVE  ILLUSTRATIONS. 


PHILADELPHIA: 

P.  BLAKISTON,  SON  &  CO., 

1012  WALNUT  STREET. 
1890. 


Copyright,  1890,  by  P.  BLAKISTON,  SON  &  Co. 


PRES8  OF   WM.    F.    FELL   <*    CO., 

1220-24  SANSOM  STREET, 

PHILADELPHIA. 


PREFACE 


In  preparing  this  little  volume  the  author  has  had 
constantly  in  view  the  needs  of  a  large  class  of  stu- 
dents of  analytical  chemistry  desirous  of  becoming 
acquainted  with  the  methods  of  quantitative  analysis 
by  electrolysis  ;  these  are  daily  acquiring  greater  im- 
portance, and  being  introduced  and  applied  wherever 
possible. 

The  larger  texts  devoted  to  analysis  have  omitted 
electrolysis  from  their  pages,  thus  rendering  its  special 
treatment  necessary  and  desirable. 

The  plan  adopted  in  the  following  pages  in  present- 
ing this  subject  has  been  to  give  a  brief  introduction 
upon  the  behavior  of  the  current  toward  the  different 
acids  and  salts,  a  short  description  of  the  various 
sources  of  the  electric  energy;  its  control  and  measure- 
ment ;  after  which  follow  a  condensed  history  of  the 
introduction  of  the  current  into  chemical  analysis,  and 
sections  relating  to  the  determination  and  separation 
of  metals,  as  well  as  the  oxidations  possible  by  means 
of  the  electric  agent. 

In  using  this  book  as  a  guide,  the  student  is  ear- 
nestly recommended  to  perform  the  determinations  of 
each  metal  as  indicated  in  the  text.  The  details  have 

v 


VI  PREFACE. 

been  made  sufficiently  full,  and  clear  enough,  it  is 
hoped,  for  the  most  inexperienced  analyst.  Additional 
skill  and  valuable  experience  are  acquired  with  each 
trial,  so  that,  when  the  section  treating  of  separations 
is  reached,  the  work  there  outlined  will  be  performed 
without  difficulty.  Before  commencing  the  determina- 
tion of  any  one  metal  read,  if  possible,  its  literature. 

The  methods  of  determination  and  separation  given 
preference  are  not  those  of  any  one  individual,  but 
have  been  selected  from  all  sources  after  an  experience 
of  many  years,  care  being  taken  to  present  only  those 
which  actual  tests  have  shown  to  be  reliable  and  trust- 
worthy. 

It  has  not  been  considered  advisable  to  include  an 
outlined  electrolytic  analysis  of  alloys  and  minerals 
in  the  text,  inasmuch  as  the  experience  gained  in  per- 
forming the  analyses  already  described  there  will  have 
given  the  analyst  such  a  fund  of  experience  that  the 
course  to  be  pursued  in  special  cases  will  readily  sug- 
gest itself. 

The  author  would  here  acknowledge  his  indebted- 
ness to  the  various  writers  on  electrolysis,  whose 
publications  he  has  freely  used,  to  the  editors  of  the 
different  journals  consulted,  to  friends  who  have  made 
kindly  suggestions,  and  to  his  brother,  Dr.  Allen  J. 
Smith,  who  prepared  all  the  drawings  from  which  the 
illustrations  of  the  text  were  made.  S. 

University  of  Pen n a., 
Philadelphia,  Sept.,  1890. 


TABLE  OF  CONTENTS. 


PAGB 

INTRODUCTION, 9-10 

ACTION  OF  THE  ELECTRIC  CURRENT  UPON  ACIDS  AND  SALTS,       10-13 

OHM,  VOLT,  AMPERE, ;  .        13-14 

SOURCES  OF  ELECTRIC  CURRENT — 

Grenet  Battery,  Leclanche  Cell,  Daniell  Cell,  Meidinger 
Cell,  Crowfoot  Cell,  Bunsen  and  Grove  Batteries, 
Magneto-Electric  Machines,  Storage  Cells,  Ther- 
mopile,    14-25 

REDUCTION  OF  THE  CURRENT — 

Rheostat,  Resistance  Frame, 25-29 

MEASURING  CURRENTS — 

Voltameter,  Amperemeter, 29-32 

HISTORICAL  SKETCH,    .* .        32-46 

SPECIAL  PART. 

1.  DETERMINATIONS  OF  METALS, 47-89 

2.  SEPARATION  OF  METALS, 89-108 

3.  OXIDATIONS  BY  MEANS  OF  THE  ELECTRIC  CURRENT,  .  108-113 
INDEX, 115 


Vll 


IO  ELECTRO-CHEMICAL   ANALYSIS. 

determinations  where  the  ordinary  methods  yield  un- 
satisfactory results.  This  statement  is  readily  con- 
firmed on  recalling  the  gravimetric  methods  usually 
employed  in  the  estimation  of  copper,  mercury,  cad- 
mium, bismuth,  tin,  etc.,  etc.  That  this  assertion  may 
be  the  conviction  of  every  student  of  analysis,  the 
writer  would  call  attention  first  to  the  course  of  the 
current  in  solutions  of  some  of  the  more  frequently 
occurring  salts;  after  which  will  follow  a  brief  account 
of  the  various  modes  of  obtaining  the  electric  current, 
how  it  may  be  measured  and  how  controlled.  Finally, 
all  the  metals,  which  have  been  studied  electrolytically, 
will  be  taken  up  in  detail,  and  their  various  determina- 
tions will  be  followed  by  a  sufficient  number  of  separa- 
tions to  show,  at  least  in  part,  how  widely  the  electro- 
lytic method  of  analysis  may  be  applied. 


i.  ACTION  OF  THE  ELECTRIC  CURRENT  UPON 
ACIDS  AND  SALTS. 

At  the  At  the 

—  Pole.  +  Pole. 

Hydrochloric  acid  -(-  the  current  =  Hydrogen  -|-  Chlorine. 
Copper  chloride       -f-    "       "        =  Cu  +  C12. 

Zinc  chloride  -f    "        "        =  Zn  +  C12. 

Nitric  acid  -f    "       "        =  H  -f  NO2  -f  O. 

In  this  last  case  the  hydrogen  further  acts  upon  more 
nitric  acid  and  produces  ammonia  (NH3)  and  water. 

Lead  nitrate  -f  the  current  =  Pb  -f  NO2  +  O. 

The  oxygen  liberated  here  attacks  a  second  molecule  of 


ACTION    OF   CURRENT   UPON  ACIDS  AND   SALTS.       I  I 

lead  nitrate,  and  produces  lead  peroxide,  Pb(NO3)2  -j- 
O2  =  PbO2,  which  deposits  upon  the  positive  elec- 
trode. 

At  the       At  the 
—  Pole.     +  Pole. 

Copper  nitrate  -}-  the  current  =  Cu  -)-  (NO3)2. 
Sulphuric  acid  +   "        "       =  H2  -f  SO4. 

Secondary  changes  frequently  occur  in  these  de- 
compositions ;  thus,  in  the  last  example  the  SO4  reacts 
with  the  water  present:  SO4  +  H2O  ==  H2SO4  -f  O, 
the  oxygen  going  to  the  positive  electrode.  In  the 
electrolysis  of  copper  sulphate,  which  is  analogous  to 
sulphuric  acid,  secondary  changes  also  occur. 

At  the      At  the 
—  Pole.    +  Pole. 

Potassium  sulphate  -|-  the  current  =  K2  -f-  SO4 

In  this  decomposition  the  liberated  potassium  acts 
upon  water,  with  the  liberation  of  hydrogen  and  the 
formation  of  potassium  hydroxide. 

Bourgoin  observed  the  following  changes  with 
formic,  acetic  and  oxalic  acids,  and  their  salts  : — 

I.  Formic  Acid. — The  decomposition  may  be  ex- 
pressed in  two  equations — 

(a)  CH202  =      H      +  (CHO  -f  O). 

—  Pole  +  Pole 

(6)  2(CHO  -f-  O)  =  CH202  +         C02. 

The  decomposition  of  sodium  formate  yields  carbon 
dioxide  and  formic  acid  at  the  anode,  and  hydrogen 
and  sodium  hydroxide  at  the  cathode. 


12  ELECTRO-CHEMICAL   ANALYSIS. 

2.  Acetic  Acid.  —  The  electrolysis  of  the  dilute  acid 
affords  ^hydrogen  at  the  negative  electrode,  and  at 
the  positive  electrode  a  mixture  of  oxygen,  carbon 
dioxide  and  a  small  quantity  of  carbon  monoxide. 

3  Oxalic  Acid.  —  The  electrolysis  of  this  acid  with 
a  current  obtained  from  four  Bunsen  cells  gave  de- 
compositions which  may  be  expressed  as  follows  :  — 

C2H2O4.2H2O  -j-  current  =  3H2  -f  2CO2  -f  O2; 
—  Pole.     +Pole. 

the  oxygen  reacts  upon  additional  acid  : 

2C2H2O4  +  2H2O  -f  O2  =  4CO2  +  4H2O, 

so  that  the  final  products  are  pure  carbon  dioxide  at 
the  positive  electrode  and  hydrogen  at  the  opposite 
pole.  The  decomposition  of  potassium  oxalate  may 
be  formulated  in  the  following  way  : 


—  Pole.    +  Pole. 

the  liberated  metal  and  the  carbon  dioxide  then  react 
further  :  — 

2H2O  -f  K2  =  2KOH  -f  H2  and  2CO2  -f  2KOH  =  2KHCO3. 

When  exposed  to  the  same  influence  ammonium 
oxalate  yields  hydrogen  at  the  negative  electrode,  and 
hydrogen  ammonium  carbonate  at  the  positive  elec- 
trode. The  latter  compound  further  breaks  down 
into  ammonia  and  carbon  dioxide. 

Succinic  acid  is  electrolysed  with  difficulty.     In  its 
decomposition  the  products  which  have  generally  been 


OHM,    VOLT    AND    AMPERE.  13 

observed  at  the  positive  electrode  were  oxygen  and 
the  two  oxides  of  carbon.     By  electrolysing  sodium 
succinate   Kekule  obtained  hydrogen  at  the  cathode, 
and  carbon  dioxide  and  ethylene  at  the  anode. 
Tartaric  acid  -f  the  current  gave  at 

—  Pole.  +  Pole. 

hydrogen  acetic  acid,  carbon  dioxide, 

carbon  monoxide  and  oxygen  ; 

while  with  potassium  tartrate  the  products  were  hy- 
drogen and  potassium  at  the  cathode  and  acid  potas- 
sium tartrate,  carbon  dioxide,  carbon  monoxide  and 
oxygen  at  the  anode.  An  alkaline  solution  of  potas- 
sium tartrate  gave  hydrogen  at  the  cathode  and  at  the 
anode,  acetic  acid,  the  oxides  of  carbon,  oxygen  and 
ethane  (C2H6). 

The  above  examples  will  suffice  to  indicate  the  na- 
ture of  the  decomposition  due  to  the  current;  they 
will  assist  very  materially  in  understanding  the 
changes  occurring  in  ordinary  electrolytic  analyses. 
For  further  particulars  in  this  direction,  consult 
Tommasi's  Traite  Theorique  et pratique  d' Electrochimie. 


2.  OHM,  VOLT  AND  AMPERE. 

These  terms  may  be  defined  as  follows : — 
The  ohm  is  the  unit  of  resistance.     Its  value  is  rep- 
resented by  a  column  of  mercury  I  sq.  mm.  in  cross- 
section,  and   106.2  cm.  in  length  at  the  temperature 


14  ELECTRO-CHEMICAL   ANALYSIS. 

The  volt  is  the  unit  of  electromotive  force  (E.  M.  F.). 
It  is  the  E.  M.  F.  which  gives  a  current  of  one  ampere 
through  a  resistance  of  one  ohm. 

The  ampere  is  the  unit  of  current.  It  is  the 
current  which,  under  an  electromotive  force  of  one 
volt,  flows  through  a  circuit  offering  a  resistance 
of  one  ohm. 

V 

A-—. 
O 


3.  SOURCES  OF  THE  ELECTRIC   CURRENT. 

The  electric  energy  required  for  quantitative  analy- 
sis has  been  variously  furnished  by  batteries  of  well- 
known  types,  magneto-electric  machines,  dynamos, 
thermo-piles,  and  electrical  accumulators  or  storage 
cells.  A  brief  description  of  some  of  these  may  be 
properly  introduced  here. 

The  Grenet  cell  or  Bichromate  Battery  (Fig.  i)  con- 
sists of  two  plates  of  carbon  (K)  and  one  of  zinc  (Z), 
movable  by  means  of  the  handle,  a.  This  is  a  con- 
venient arrangement,  as  it  allows  of  easy  interruption 
of  the  current.  The  liquid  to  be  used  in  this  cell  con- 
sists of  potassium  bichromate  (i  lb.),  strong  sulphuric 
acid  (2  Ibs.),  and  water  (12  Ibs.).  In  mixing  these,  the 
probable  chemical  change  is  : — 

K,Cr207  +  7H2S04  =  2Cr03  +  K,SO4  +  H2O  +  6H2SO4. 


SOURCES   OF   THE   ELECTRIC   CURRENT.  15 

The  chemical  action  in  the  cell,  when  the  current 
passes,  may  be  expressed  by  the  equation  : — 


2CrO3  +  6H2SO4 


-f 


4  -f-  6H2O. 


The  writer  found  four  cells  of  this  type  (capacity 
two  quarts)  very  serviceable  in  the  electrolysis  of  solu- 
tions of  cadmium,  uranium,  molybdenum  and  other 


FIG.  i. 


metals.  No  disagreeable  fumes  arise  from  cells  of 
this  class.  The  electromotive  force  is  about  two 
volts,  and  the  internal  resistance  low.  The  Grenet 
cell  loses  in  intensity  when  used  for  long  periods,  but 
regains  its  value  when  it  has  remained  out  of  action 
for  some  time. 


i6 


ELECTRO-CHEMICAL   ANALYSIS. 


Leclanche  cell  (Figs.  2  and  3). —  Two  forms  of  this 
cell  are  in  use.  In  the  first,  to  the  left  of  the 
figure,  there  is  a  zinc  rod,  immersed  in  a  solution 
of  ammonium  chloride,  and  a  carbon  plate  inside 
a  porous  cup,  tightly  packed  with  a  mixture  of 
manganese  dioxide  and  broken  gas  carbon.  The 


FIG.  2. 


FIG.  3. 


porous  cup  is  only  intended  to  hold  the  mixture 
in  position.  There  is  but  one  liquid,  and  that  a 
strong  solution  of  ammonium  chloride.  The  E.  M.  F. 
of  this  cell  equals  1.47  volts;  it  decreases  rapidly 
when  sending  strong  currents.  It  is  inferior  to  the 
Daniell  cell  when  a  steady  current  is  desired  for 
a  long  period. 


SOURCES   OF   THE    ELECTRIC    CURRENT.  1 7 

The  chemical  action  in  cells  of  this  kind  Ayrton 
expresses  as  follows  : — 

(Before  sending  the  current) — 

kC+  I  (MnO2)  +  m  (NH4C1)  +  n  Zn. 
(After  sending  the  current) — 

k  C  +  (/-  2)(Mn02)  +  (m  —  2)(NH4C1)  +  (Mn.2O3)  +  2(NH3) 
+  (H20)  +  (ZnCl2)  +  (n  -  i)(Zn). 

The  letters  k,  /,  m,  n  represent  indefinite  amounts 
of  the  acting  substances. 

In  the  modified  Leclanche  cell  the  porous  cup  is 
not  needed,  as  compressed  prisms  of  manganese  diox- 
ide, gas  carbon  and  shellac  are  used  around  the 
carbon  plate. 

The  Daniell  cell  (Fig.  4)  consists  of  a  glass  jar,  the 
porous  cup  T,  and  a  cylinder  of  zinc  (Z),  the  negative 
pole.  Outside  of  the  porous  cup  is  the  sheet-copper 
cylinder  K.  The  zinc  is  the  negative  electrode,  and 
the  copper  the  positive  electrode.  The  zinc  stands  in 
dilute  sulphuric  acid  (i  :  20),  and  the  copper  in  copper 
sulphate.  Zinc  sulphate  often  replaces  the  sulphuric 
acid.  The  chemical  action  in  the  cell  is  probably : — 

k  (Cu)  -f  /  (CuSO4).  /Before  sending\   .2          m  (ZnSO*)  +  n  (Zn). 

\   the  current.    /   *S 

o. 

(k  +  i)(Cu)  +  (/  -  i)(CuS04).    /After  sendingN      §  (m  +  i)(ZnSO4  +  («  -  i)(Zn). 
V  the  current.  )      £  (Ayrton). 

PU 

The  E.  M.  F.  of  this  cell  is  about  1.07.  The  Meid- 
inger  (Fig.  5)  and  Crowfoot  (Fig.  6)  cells  are  modifica- 
tions of  the  Daniell,  and  very  serviceable  in  electrolytic 


i8 


ELECTRO-CHEMICAL   ANALYSIS. 
FIG.  4. 


SOURCES   OF   THE   ELECTRIC    CURRENT.  \g 

work  when  currents  of  low  intensity  are  desired.  In 
the  sketch  of  the  Meidinger  cell,  G  is  a  large  glass 
jar;  gt  a  small  glass  vessel,  in  which  stands  the  copper 
cylinder,  K  (-f-  P).  Z  ( —  P)  is  a  cylinder  of  zinc. 
B  contains  the  supply  of  copper  sulphate  crystals. 

The  current  from  either  of  these  batteries  remains 
quite  constant  for  long  periods.  The  cells  themselves 
do  not  require  much  attention.  Haifa  dozen  of  either 
of  these  forms  will  do  nearly  all  the  electrolytic  work 
of  an  ordinary  laboratory.  The  "Crowfoot"  form 
can  be  readily  and  cheaply  prepared.  Rejected  acid 
bottles,  after  removing  the  neck  and  upper  portions, 
answer  well  as  jars. 

If  currents  of  greater  E.  M.  F.  are  required,  the 
Bunsen  (Fig.  7)  or  Grove  cell  (Fig.  8)  should  be  used. 
*  In  the  former  there  is  zinc  in  dilute  sulphuric  acid,  or 
a  mixture  of  potassium  bichromate  and  sulphuric  acid, 
and  a  carbon  plate  in  a  cup  of  nitric  acid.  It  is  a  less 
expensive  cell  than  the  Grove,  as  platinum  is  not 
employed.  It  is  not  so  readily  handled,  and  con- 
sumes more  nitric  acid.  Its  electromotive  force  is 
somewhat  less  than  that  of  the  Grove  form.  In  the 
latter  there  is  a  strip  of* platinum  (P)  in  concentrated 
nitric  acid  (in  the  porous  cup,  x)~  and  zinc  (ZZ)  in 
dilute  sulphuric  acid  (one  pint  acid  and  ten  pints 
water).  The  E.  M.  F.  is  1.93  volts.  When  acting, 
X2O4  is  set  free ;  this  can  be  in  a  measure  suppressed 
by  adding  ammonium  chloride  to  the  nitric  acid. 
The  chemical  changes  occurring  in  the  Bunsen  and 


20 


ELECTRO-CHEMICAL   ANALYSIS. 


Grove  cells  are  very  similar.     Ayrton  expresses  them 
as  follows : — 


(Befor^  current  is  sent) — 

A(Pt)  +/(HN03). 
(After  sending  current) — 
*  (Pt)  +  (/—  2)(HN08)  +  (N2O4)  +  (2H20). 


FIG.  7. 


The  internal  resistance  of  the  Grove  cell  is  small. 
To  obtain  good  results  both  the  Bunsen  and  Grove 
cells  require  constant  attention. 


SOURCES    OF   THE    ELECTRIC    CURRENT.  21 

In  amalgamating  the  zincs  in  any  of  the  preceding 
batteries,  first  allow  them  to  remain  o,ver  night  in  very 
dilute  hydrochloric  acid,  then  immerse  in  mercury, 
and  with  a  wet  cloth  rub  the  latter  into  the  metal. 
This  should  be  done  once  a  week,  when  the  cells  are 
in  daily  use.  For  further  information  upon  batteries, 
consult  Ayrton's  Practical  Electricity. 

Magneto-electric  machines,  and  dynamos  have  been 
used  to  some  extent  in  electrolytic  decompositions, 
but  a  detailed  description  of  their  construction  will 
not  be  given.  This  may  be  found  in  Classen's 
Analysis  by  Electrolysis,  pp.  21-35  (Herrick's  transla- 
tion). 

Thermo-piles  have  also  been  used  to  furnish  cur- 
rents for  electrolytic  work.  Their  use  has  been 
objected  to  upon  the  ground  that  the  currents  afforded 
by  them  are  rarely  strong  enough  for  the  greater  num- 
ber of  determinations  and  separations,  and  again  they 
are  easily  broken  and  difficult  to  repair.  The  forms 
generally  met  with  are  those  recommended  by  Cla- 
mond  and  Noe. 

The  Clamond  thermo-pile  is  pictured  in  Fig.  9.  I 
is  a  perspective  view  of  the  same ;  2  represents  a  ver- 
tical section,  and  3  a  basal  section,  showing  the  bars 
and  armatures.  The  elements  consist  of  bars  of  a  zinc 
and  antimony  alloy,  and  a  strip  of  sheet-iron.  These 
are  arranged  in  circles,  as  indicated  in  3  ;  they  are 
placed  one  above  the  other.  In  3,  B  represents  the 
bars  of  zinc  and  antimony  alloy,  while  the  tinned 


22 


ELECTRO-CHEMICAL   ANALYSIS. 


SOURCES    OF    THE    ELECTRIC    CURRENT.  23 

sheet-iron  plates  are  marked  L.  The  sheet-iron  serves 
to  conduct  the  current  from  one  element  to  the  other; 
hence,  these  strips  rest  upon  the  bars  B.  Heat  ex- 
pands the  latter,  and  in  consequence  renders  the  con- 
tact more  intimate.  The  single  elements,  as  well  as 
the  circles  of  elements,  are  separated  from  each  other 
by  plates  of  asbestos  (see  r  in  2).  The  cylinder  itself 
consists  of  a  series  of  such  circles.  The  welded  points 
of  the  bars  are  all  directed  to  the  centre  of  the  cylin- 
der. The  gas  flames  are  prevented  from  coming  in 
immediate  contact  with  them  by  the  asbestos  lining 
of  the  cylinder.  As  gas  is  employed  to  furnish  the 
necessary  heat,  in  the  middle  of  the  cylinder  will  be 
observed  a  clay  tube  (A)  provided  with  apertures  (2 
and  3).  The  gas  enters  through  the  Giroud  regulator 
C  (i  and  2),  which  makes  it  possible  to  maintain  a 
uniform  temperature,  and  a  constant  current.  From 
C  it  is  conducted  to  A,  through  7",  into  which  air  is 
admitted  by  suitable  apertures.  The  mixture  of  air 
and  gas  burns  at  the  openings  in  A.  Additional 
air  is  supplied  through  D.  Light  the  gas  jets  from 
above,  after  removing  the  cover.  The  poles  of  each 
ring  of  elements  end  in  binding  screws,  thus  en- 
abling the  operator  to  connect  any  number  of  them, 
depending  upon  the  external  resistance  (Z.  f.  a.  Ch., 

15,  334)- 

When  in  excellent  condition,  thermo-piles  are  said 
to  yield  a  current  equivalent  to  400-500  c.c.  oxy- 
hydrogen  gas  per  hour.  Those  persons  who  may 


24  ELECTRO-CHEMICAL    ANALYSIS. 

desire  fuller  information  upon  this  type  of  battery  are 
referred  to  the  following 

LITERATURE: — Z.  f.  a.  Ch.,  14,  350;    17,  205;    Ding.  p.  Jr.,  224, 
267;  Z.  f.  a.  Ch.,  18,  457;   25,  539. 

The  best  source  of  electric  energy,  for  electrolytic 
purposes,  is  unquestionably  the  storage  cell  (Fig.  10). 

FIG.  10. 


The  illustration  represents  a  cell  of  the  Julien  type. 
It  contains  nineteen  alternating  plates  of  lead  and  lead 
dioxide.  Each  of  these  is  five  and  three-fourths  inches 
square.  The  exciting  liquid  is  sulphuric  acid  of  sp. 
gr.  1.2.  The  E.  M.  F.  of  such  a  cell  is  a  little  more 
than  two  volts.  The  current  is  very  constant. 

Cells  of  this  kind  can   be  charged    from   primary 


REDUCTION  OF  THE  CURRENT.          25 

batteries,  or  better,  by  means  of  a  dynamo.  In  any 
community  where  electric  lighting  is  employed  it  is 
possible  to  have  the  charging  done  at  little  expense, 
and  in  factories  where  there  is  always  sufficient  power, 
a  small  dynamo  could  easily  be  arranged  for  this  pur- 
pose, so  that  almost  any  number  of  cells  could  be  kept 
in  condition  for  work.  The  iron  estimations  required 
by  any  establishment  could  be  rapidly  and  accurately 
made  with  three  cells  of  this  type ;  little  attention 
would  be  demanded  from  the  chemist.  While  storage 
cells  can  be  used  in  almost  every  description  of  elec- 
trolysis, there  are  a  great  many  cases  where  economy 
would  suggest  the  use  of  the  cheaper  batteries,  e.g., 
the  Crowfoot.  Consult  the  following  literature  upon 
storage  batteries: — 

Proceedings  of  the  Royal  Society,  June  2Oth,  1889;  Transactions  of 
Am.  Inst.  Mining  Engineers  (Electrical  Accumulators,  Salom),  Feb., 
1890. 

Having  thus  briefly  described  the  more  important 
current-producers,  the  means  of  regulating  the  current 
may  be  next  considered. 


4.  REDUCTION  OF  THE  CURRENT. 
When  a  battery  gives  a  current  that  generates  10 
c.c.  oxy-hydrogen  gas  per  minute,  and  work  is  to  be 
done  which  can  easily  be  performed  by  an  expenditure 
of  energy  not  exceeding  3  c.c.  oxy-hydrogen  gas  per 
minute,  it  will  become  necessary  to  reduce  the  strong 
c 


26 


ELECTRO-CHEMICAL   ANALYSIS. 


current.  Persons  acquainted  with  practical  physics 
will  promptly  suggest  the  resistance  coils  found  in 
physical  laboratories,  as  suitable  for  this  purpose. 
They  are,  on  the  whole,  quite  satisfactory,  and  have 
been  thus  utilized,  although  simpler  and  more  con- 
venient current-reducers  have  made  their  appearance 

FIG.  ii. 


in  recent  years.     A  few  of  these  later  appliances  may 
be  mentioned : — 

i.  The  current  may  be  sent  through  a  solution 
(saturated)  of  zinc  sulphate,  contained  in  a  large  glass 
cylinder,  about  22  cm.  long  and  8.5  cm.  in  diameter. 
In  one  experiment  the  current  is  passed  from  a  to  b 
(Fig.  T  i),  and  in  the  next  from  b  to  a.  "  The  rod  b, 


REDUCTION  OF  THE  CURRENT.          2/ 

with  one  zinc  pole,  is  pushed  toward  the  zinc  pole  a, 
until  the  current  reaches  the  desired  strength."  It  is 
well  to  amalgamate  the  zincs  from  time  to  time.  We 
are  indebted  for  this  piece  of  apparatus  to  Classen, 
who  has  also  described  another  simple  rheostat  (Fig. 
12)  (Ben,  21,  359).  In  this  apparatus  the  current 
enters  at  a,  travels  the  German  silver  resistance  ;/,  and 
returns  through  b  to  the  battery.  In  the  performance 
of  electrolytic  depositions  the  platinum  vessels,  serv- 


ing as  negative  electrodes,  may  be  connected  with  any 
one  of  the  binding-posts  from  1-20.  This  makes  it 
possible  for  the  analyst  to  execute  eight  different  de- 
terminations at  the  same  time.  To  show  the  influence 
of  this  apparatus,  a  current  from  five  Bunsen  cells, 
generating  68  c.c.  oxy-hydrogen  gas  per  minute,  was 
allowed  to  act  upon  copper  solutions  contained  in  six 
vessels.  The  current  at  binding-post  I  was  found  to 
be  equal  to  3.75  amperes;  at  2,  it  equaled  2.617 


28 


ELECTRO-CHEMICAL   ANALYSIS. 


P^JG.    13. 


MEASURING    CURRENTS.  29 

amperes;  at  3,  2.085  amperes;  at  4,  1.911  amperes, 
etc.,  until  at  20  it  was  only  0.098  of  an  ampere. 

To  better  understand  these  figures  it  should  be  re- 
membered that  an  ampere  equals  10.436  c.c.  oxy- 
hydrogen  gas  per  minute,  or  it  is  equivalent  to  a 
current  which  will  precipitate  19.69  mg.  of  metallic 
copper,  or  67.1  mg.  of  metallic  silver  in  one  minute. 

For  a  larger  form  of  apparatus  somewhat  similar  to 
that  described  above  see  Ber.,  17,  1787. 

The  writer  has  for  some  time  employed  a  much 
simpler  current-reducer,  which  has  the  advantage  of 
cheapness  and  ready  construction  to  recommend  it. 
It  consists  of  a  light  wooden  parallelogram,  about  six 
feet  in  length.  Extending  from  end  to  end,  on  both 
sides,  is  a  light  iron  wire,  measuring  in  all  about  500 
feet  (Fig.  13).  With  the  binding-posts  at  a  and  b,  and 
a  simple  clamp,  it  is  possible  to  throw  in  almost  any 
resistance  that  may  be  required.  It  answers  all  prac- 
tical purposes. 

LITERATURE. — v.  Klobukow,  Jr.  f.  pkt.  Ch.,  37,  375;  40,  121. 


5.  MEASURING  CURRENTS,  VOLTAMETER, 
AMPEREMETER. 

In  every  analysis  by  electrolysis  it  is  advisable  that 
the  strength  of  the  acting  current  should  be  known. 
The  simplest  and  most  convenient  apparatus  for  this 
purpose  is  the  Bunsen  voltameter  (Fig.  14).  The 
inner  tube  a,  containing  sulphuric  acid  of  sp.  gr.  1.22, 


3O  ELECTRO-CHEMICAL   ANALYSIS. 

stands  in  a  large  cylinder  of  water  to  cool  it.  The 
liberated  hydrogen  and  oxygen  are  collected  over 
water  in  the  eudiometer  tube  R ;  p  and  pr  are  platinum 
electrodes.  In  all  accurate  experiments  the  volume 
of  gas  should  always  be  reduced  to  o°  and  760  mm. 

•FIG.  14. 


pressure.  Some  chemists  substitute  a  galvanometer 
(tangent  or  sine)  for  the  voltameter.  The  deflection 
of  the  needle  by  the  current  measures  the  strength  of 
the  latter.  "  In  order  to  express  in  terms  of  chemical 
action  the  deflection  of  the  needle,  it  is  placed  in  the 


MEASURING    CURRENTS.  3! 

same  current  with  a  voltameter,  and  the  deviation  of 
the  needle  is  observed,  as  well  as  the  volume  of  elec- 
trolytic gas  (reduced  to  o°  and  760  mm.  pressure), 
which  is  produced  in  a  minute.  Placing  the  volume 
equal  to  v,  the  quotient  ~  -  gives  the  standard  value 
for  the  galvanometer.  If  this  standard  value  is  de- 

FIG.  15. 


noted  by  R,  the  strength  I,  of  a  current,  which  pro- 
duces the  deviation  a,  is  I  =  R  tan.  a." 

The  writer  has  found  the  amperemeter  of  Kohl- 
rausch  (Fig.  15)  very  satisfactory,  especially  in  cases 
where  strong  currents  are  employed.  In  this  instru- 
ment the  current  travels  through  an  insulated  wire 


32  ELECTRO-CHEMICAL    ANALYSIS. 

surrounding  a  bar  of  soft  iron.  The  latter,  in  its 
magnetized  state,  attracts  the  needle  C,  attached  to  a 
spiral.  C  moves  over  a  graduated  face  (in  amperes), 
and  its  deflection  gives  at  once  the  strength  of  the 
current  in  amperes. 

In  electrolytic  work  of  any  kind  it  is  advisable 
that  the  apparatus  intended  to  measure  the  current 
strength  should  be  in  the  circuit  during  the  entire 
decomposition,  for  it  is  only  in  this  way  that  we  can 
expect  to  effect  separations  without  encountering  un- 
pleasant difficulties.  It  is  necessary  to  know  just  what 
energy  is  required,  and  then  to  so  regulate  the  current 
that  the  same  is  approximately  maintained  throughout 
the  entire  determination. 

Before  taking  up  the  description  of  the  details  to 
be  observed  in  the  electrolytic  precipitation  of  indi- 
vidual metals,  it  may  not  be  uninteresting  to  briefly 
trace  the  history  of  the  introduction  of  the  electric 
current  into  chemical  analysis. 


6.  HISTORICAL. 

Although  the  early  years  of  this  century  show  con- 
siderable activity  in  electrical  studies,  the  efforts  were 
mainly  directed  to  the  solution  of  the  physical  side  of 
electrolysis.  To  Gaultier  de  Claubry  probably  be- 
longs the  credit  of  having  first  (1850)  applied  the  cur- 
rent to  the  detection  of  metals  when  in  solution.  His 
efforts  were  wholly  directed  to  the  isolation  of  metals 


HISTORICAL.  33 

from  poisons  by  depositing  the  same  upon  plates  of 
platinum.  When  the  precipitation  was  considered 
finished  the  plates  were  removed,  carefully  washed, 
and  the  deposited  metals  brought  into  solution  with 
nitric  acid,  and  there  tested  for  and  identified  by  the 
usual  course  of  analysis.  The  current  was  evidently 
very  feeble,  as  the  time  recorded  as  necessary  for  the 
deposition  varied  from  ten  to  twelve  hours.  Gaultier 
considered  this  method  reliable  in  all  instances,  but 
especially  recommends  it  for  the  separation  of  copper 
from  bread.  In  testing  for  zinc  he  employed  a  strip 
of  tin  as  anode,  but  states  that  a  platinum  plate  will 
answer  as  well. 

In  Graham-Otto's  Lehrbuch  der  Chemie  (1857)  it 
is  stated  that  the  oxygen  developed  at  the  positive 
electrode  readily  induces  the  formation  of  peroxides ; 
.  .  .  that  lead  and  manganese  peroxides  are  de- 
posited, from  solutions  of  these  metals,  upon  the  posi- 
tive electrode  of  the  battery ;  .  .  .  that  the  point  of 
a  platinum  wire,  when  attached  to  the  anode  of  a  cell, 
is  therefore  a  delicate  means  of  testing  for  manganese 
and  lead.  In  the  same  text  the  oxidizing  power  of 
the  anode  is  nicely  shown  by  the  following  simple  ex- 
periment :  A  piece  of  iron,  in  connection  with  the 
positive  electrode  of  the  battery,  is  introduced  into  a 
V-shaped  glass  tube  containing  a  concentrated  solu- 
tion of  potassium  hydroxide,  while  a  platinum  wire 
running  from  the  negative  electrode  projects  into  the 
other  limb  of  the  vessel.  In  a  short  time  ferric  acid 


34  ELECTRO-CHEMICAL   ANALYSIS. 

appears  around  the  anode,  and  is  recognized   by  its 
color. 

C.  Despretz  (1857)  described  the  decomposition  of 
certain  salts  by  means  of  the  electric  current,  and 
remarked  that,  while  operating  with  solutions  of  the 
acetates  of  copper  and  lead,  he  expected  both  metals 
would  be  deposited  upon  the  negative  pole,  and  was 
much  surprised  to  find  that  the  lead  separated  as  oxide 
upon  the  anode  at  the  same  time  that  the  copper 
was  deposited  upon  the  cathode.  The  results  were 
the  same  when  experiments  were  conducted  with 
the  nitrates  and  pure  acetates.  With  manganese  no 
deposition  took  place  upon  the  negative  electrode,  but 
a  black  oxide  appeared  at  the  opposite  pole.  Potas- 
sium antimonyl  tartrate  gave  a  crystalline  metallic 
deposit  of  antimony  at  the  cathode,  and  upon  the  anode 
a  yellowish-red  coating,  supposed  to  be  anhydrous 
antimonic  acid.  Bismuth  nitrate  yielded  a  reddish- 
brown  deposit  at  the  positive  electrode.  Despretz 
concludes  his  paper  by  stating  that  although  the  facts 
were  few  in  number,  yet  they  were  new  in  so  far  as 
they  concerned  lead,  antimony  and  manganese ;  and, 
furthermore,  that  the  separation  of  copper  from  lead 
by  the  current  was  almost  perfectly  complete. 

Three  years  later  (1860)  Charles  L.  Bloxam  recom- 
mended the  process  of  Gaultier  for  the  detection  of 
metals  in  organic  mixtures,  although  it  may  not  be 
improper  to  add  that  Smee  (1851),  in  his  work  on 
electrometallurgy,  asserts  that  Morton  was  the  first 


HISTORICAL.  35 

person  to  employ  the  electric  current  for  the  isolation 
of  metals  from  poisonous  mixtures.  However  this 
may  be,  the  fact  remains  that  Bloxam  did  use  the 
current  quite  extensively  for  this  purpose,  and  while 
he  claims  no  quantitative  results  for  the  method,  the 
apparatus  employed  by  him  and  his  subsequent  work 
in  this  direction  deserve  great  credit. 

To  detect  arsenic  electrolytically  Bloxam  made  use 
of  a  glass  jar,  four  cubic  inches  in  capacity,  closed 
below  by  parchment,  which  was  tightly  secured  by 
means  of  a  thin  platinum  wire.  In  the  neck  of  the 
jar  was  a  large  cork,  through  which  passed  a  glass 
tube  bent  at  a  right  angle.  This  tube  was  intended 
to  serve  as  a  means  of  escape  for  the  gases  liberated 
within  the  jar.  The  platinum  wire  from  the  negative 
electrode  was  also  held  in  position  by  the  cork.  The 
portion  of  the  wire  within  the  jar  was  attached  to  a 
platinum  plate  dipping  into  the  arsenical  mixture  con- 
taining dilute  sulphuric  acid.  The  jar  with  its  contents 
stood  in  a  wide  beaker,  filled  with  water,  into  which 
dipped  the  positive  electrode  of  the  battery.  Under 
the  influence  of  the  current,  metals  like  antimony, 
copper,  mercury  and  bismuth  separated  upon  the 
platinum  plate  of  the  negative  electrode,  while  arsine 
was  liberated  and  escaped  through  the  exit-tube  into 
some  suitable  absorbing  liquid.  To  ascertain  what 
metal  or  metals  had  separated  upon  the  cathode, 
the  plate  attached  thereto  was  removed,  after  the 
interruption  of  the  current,  and  treated  with  hot 


36  ELECTRO-CHEMICAL    ANALYSIS. 

ammonium  sulphide.  Upon  evaporating  this  solution 
an  orange-colored  spot  remained  if  antimony  had  been 
previously  present.  If  a  metallic  deposit  continued 
to  adhere  to  the  foil  the  latter  was  acted  upon  by 
nitric  acid  to  effect  the  solution  of  the  remaining 
metals. 

J.  Nickles  (1862)  precipitated  silver  with  the  current 
obtained  from  a  zinc-copper  couple.  The  positive 
electrode  consisted  of  a  piece  of  graphite,  taken  from 
a  lead-pencil,  while  a  thin,  bright  copper  wire  consti- 
tuted the  negative  electrode.  The  silver  separated 
upon  this.  The  current  was  very  feeble,  for  hydrogen 
was  not  liberated  at  the  cathode.  Nickles  also  sug- 
gested the  reduction  of  large  quantities  of  silver  from 
the  solution  of  its  cyanide  by  this  means.  To  obtain 
the  silver  he  advised  using  a  cylindrical  cathode  con- 
structed from  some  readily  fusible  alloy,  so  that  after 
the  reduction  was  finished,  the  other  metals  might  be 
easily  melted  out  and  leave  a  silver  plate.  Copper, 
lead,  bismuth  and  antimony  were  separated  electro- 
lytically,  by  Nickles,  from  textiles. 

In  1862  A.  "C.  and  E.  Becquerel  resumed  their 
electro-chemical  investigations,  first  begun  some  thirty 
years  previously.  Their  experiments  seem  to  have 
been  aimed  chiefly  toward  the  reduction  of  metallic 
solutions  upon  a  large  scale,  caring  not  for  the  quanti- 
tative estimation  of  metals,  but  seeking  rather  a  rapid 
and  satisfactory  technical  isolation  process. 

Wohler   (1868)   found   that   when   palladium    was 


HISTORICAL.  37 

made  the  positive  conductor  of  two  Bunsen  cells,  and 
placed  in  water  acidulated  with  sulphuric  acid,  it 
immediately  became  covered  with  alternating,  bright, 
steel-like  colors.  He  regarded  the  coating  as  palladium 
dioxide  since  it  liberated  chlorine  when  treated  with 
hydrochloric  acid,  and  carbon  dioxide  when  warmed 
with  oxalic  acid.  Black  amorphous  metal  separated 
at  the  cathode.  Its  quantity  was  slight.  Under 
similar  conditions  lead  also  yields  the  brown  dioxide, 
and  the  same  may  be  said  of  thallium.  Osmium,  in 
its  ordinary  porous  form,  at  once  becomes  osmic  acid. 
When  caustic  alkali  is  substituted  for  the  acid  the 
liquid  rapidly  assumes  a  deep  yellow  color,  while  a 
thin  deposit  of  metal  appears  upon  the  cathode. 
Ruthenium  behaves  similarly  when  applied  in  the 
form  of  powder.  Osmium-iridium,  a  compound  de- 
composed with  difficulty  under  ordinary  circum- 
stances, immediately  passes  into  solution  when  brought 
in  contact  with  the  positive  electrode  of  a  battery 
placed  in  a  solution  of  sodium  hydroxide,  and  imparts 
a  yellow  color  to  the  alkaline  liquid.  A  black 
deposit  of  metal  slowly  makes  its  appearance  upon 
the  negative  pole. 

The  experiments,  thus  far  described,  are  qualitative 
in  their  results.  The  first  notice  of  the  quantitative 
estimation  of  metals  electrolytically  was  that  of  Gibbs 
(1864),  when  he  published  the  results  he  had  obtained 
with  copper  and  nickel.  Luckow,  in  alluding  to  this 
work  a  year  later  (1865),  says  :  "  I  take  the  liberty  to 


38  ELECTRO-CHEMICAL   ANALYSIS. 

observe  that  so  far  as  the  determination  of  copper  is 
concerned,  I  estimated  that  metal  in  this  manner 
more  than  twenty  years  ago,  and  as  early  as  1860 
employed  the  electric  current  for  the  deposition  of 
copper  quantitatively  in  various  analyses."  It  was 
Luckow  who  proposed  the  name  Elektro-Metall  Ana- 
lyse for  this  new  method  of  quantitative  analysis. 
According  to  this  writer  the  current  may  be  applied 
as  follows : — 

1.  To  dissolve  metals  and  alloys  in  acids  by  which 
they  would  not  be  affected  unaided  by  the  electric 
current. 

2.  To    detect    metals    like    manganese    and    lead 
(silver,  nickel,  cobalt) ;   separating  them  in  the  form 
of  peroxides ;  also  manganese  as  permanganic  acid. 

'  3.  To  separate  various  metals,  e.g.,  copper  and 
manganese  from  zinc,  iron,  cobalt  and  nickel. 

4.  To   deposit  and  estimate   metals   quantitatively, 
in  acid,  alkaline  and  neutral  solutions. 

5.  For  various  reductions,  e.g.,  silver  chloride,  basic 
bismuth  chloride  and  lead  sulphate,  in  order  that  the 
metals  in  them  may  be  determined.     To  reduce  chro- 
mic acid  to  oxide,  e.  g.,  potassium  bichromate  acidu- 
lated with  dilute  sulphuric  acid. 

These  applications  embrace  nearly  all  that  has  since 
been  accomplished  by  the  aid  of  the  current.  In  the 
same  article  to  which  Luckow  calls  attention  to  the 
facts  recorded  above,  he  describes  minutely  the  method 


HISTORICAL.  39 

pursued  by  him  in  the  precipitation  of  metals.  Refer- 
ence to  these  early  experiments  will  show  with  what 
care  and  accuracy  every  detail  was  worked  out. 
Luckow  also  announced  "  that  all  the  lead  contained 
in  solution  was  deposited  as  peroxide  upon  the  posi- 
tive electrode,  and  might  be  determined  from  the 
increased  weight  of  the  latter."  This  observation 
was  fully  confirmed  by  Hampe  and,  later,  by  W. 
C.  May. 

Wrighfson  (1876)  called  attention  to  the  fact  that 
if  solutions  of  copper  were  electrolysed  in  the  presence 
of  other  metals,  the  latter  greatly  influenced  the  sepa- 
ration of  the  former.  For  example,  with  copper  and 
antimony,  the  deposition  of  the  copper  was  always 
incomplete  when  the  antimony  equaled  one-fourth  to 
two-thirds  the  quantity  of  the  former.  Notwithstand- 
ing, a  complete  separation  of  the  two  metals  can  be 
effected  when  the  quantity  of  the  antimony  is  small. 
A  somewhat  similar  behavior  was  noticed  with  other 
metals.  The  deposition  of  cadmium,  zinc,  cobalt  and 
nickel  was  apparently  not  satisfactory. 

Lecoq  de  Boisbaudran  (1877)  electrolysed  the  potas- 
sium hydroxide  solution  of  the  metal  gallium,  using 
six  Bunsen  elements  with  20-30  c.c.  of  the  concen- 
trated liquid.  The  deposited  metal  was  readily  de- 
tached when  the  negative  electrode  was  immersed  in 
cold  water,  and  bent  slightly. 

The  unpromising  behavior  of  zinc  solutions,  ob- 
served by  Wrightson,  was  fortunately  overcome  by 


40  ELECTRO-CHEMICAL   ANALYSIS. 

Parodi  and  Mascazzini  (1877),  who  employed  a  solu- 
tion of  the  sulphate,  to  which  was  added  an  excess  of 
ammonium  acetate.  Lead  was  also  deposited  in  a 
compact  form  from  an  alkaline  tartrate  solution  of  this 
metal  in  the  presence  of  an  alkaline  acetate. 

•After  Luckow's  experiments  upon  manganese,  little 
attention  appears  to  have  been  given  this  metal  until 
Riche  (1878)  published  his  results.  While  confirming 
the  observations  of  Luckow,  he  discovered  that  manga- 
nese was  not  only  completely  precipitated  from  the 
solution  of  its  sulphate,  but  also  from  that  of  the 
nitrate,  thus  rendering  possible  an  electrolytic  sepa- 
ration of  manganese  from  copper,  nickel,  cobalt,  zinc, 
magnesium,  the  alkaline  earth  and  the  alkali  metals. 
Riche  recommended  that  the  deposited  dioxide  be 
carefully  dried,  converted  by  ignition  into  the  proto- 
sesquioxide  and  weighed  as  such.  According  to  this 
chemist,  the  one-millionth  of  a  gram  of  manganese, 
when  exposed  to  the  action  of  the  current,  gave  a 
distinct  rose-red  color,  perceptible  even  when  diluted 
tenfold. 

In  zinc  depositions  Riche  gave  preference  to  a 
solution  of  zinc- ammonium  acetate  containing  free 
acetic  acid. 

Luckow  was  the  first  to  mention  that  the  current 
caused  mercury  to  separate  in  a  metallic  form,  from 
acid  solutions,  upon  the  negative  electrode.  F.  W. 
Clarke  (1878)  used  a  mercuric  chloride  solution, 
feebly  acidulated  with  sulphuric  acid,  for  this  purpose. 


HISTORICAL.  41 

The  deposition  was  made  in  a  platinum  dish,  using 
six  Bunsen  cells.  Mercurous  chloride  was  at  first  pre- 
cipitated, but  it  was  gradually  reduced  to  the  metallic 
form.  J.  B.  Hannay  (1873)  had  previously  recom- 
mended precipitating  this  metal  from  solutions  of 
mercuric  sulphate,  but  gave  no  results. 

Clarke,  also,  gave  some  attention  to  cadmium ;  his 
results,  however,  were  not  satisfactory.  A  few 
months  later  the  writer  (1878)  succeeded  in  depositing 
cadmium  completely  and  in  a  very  compact  form 
from  solutions  of  its  acetate.  Upon  this  behavior 
Yver  (1880)  based  his  separation  of  cadmium  from 
zinc.  Furthermore,  the  writer  found  (1880)  that  the 
deposition  of  cadmium  could  be  made  from  solutions 
of  its  sulphate,  contrary  to  an  earlier  observation  of 
Wrightson.  At  the  same  time  copper  was  completely 
separated  from  cadmium  by  electrolysing  their  solu- 
tion in  the  presence  of  free  nitric  acid. 

A  very  successful  determination  of  both  zinc  and 
cadmium  was  published  by  Beilstein  and  Jawein  in 
1879.  They  employed  for  this  purpose  solutions  of 
the  double  cyanides. 

Heinrich  Fresenius  and  Bergmann  (1880)  found 
that  the  electrolysis  of  nickel  and  cobalt  solutions 
succeeded  best  in  the  presence  of  an  excess  of  free 
ammonia  and  ammonium  sulphate. 

Their  experience  with  silver  demonstrated  that 
the  best  results  could  be  obtained  with  solutions 


42  ELECTRO-CHEMICAL   ANALYSIS. 

containing  free  nitric  acid,  and  by  the  employment 
of  weak  currents. 

The  writer  showed  (1880)  that  if  uranium  acetate 
solutions  were  electrolysed  the  uranium  was  com- 
pletely precipitated  as  a  hydrated  protosesquioxide ; 
and  further,  that  molybdenum  could  be  deposited  as 
hydrated  sesquioxide  from  warm  solutions  of  am- 
monium molybdate  in  the  presence  of  free  ammonia. 
Very  promising  indications  were  obtained  with  salts 
of  tungsten,  vanadium  and  cerium. 

In  a  more  recent  (1880)  communication  from 
Luckow,  to  whom  we  are  indebted  for  much  that  is 
valuable  in  electrolysis,  is  given  a  full  description  of 
his  observations  in  this  field  of  analysis,  from  which 
the  following  condensed  account  is  taken.  While  it 
relates  more  particularly  to  the  qualitative  behavior 
of  various  compounds,  its  importance  demands  careful 
study. 

When  the  current  is  conducted  through  an  acid 
solution  of  potassium  chromate  the  chromic  acid  is 
reduced  to  oxide,  whereas,  if  the  solution  of  the  oxide 
in  caustic  potash  be  subjected  to  a  like  treatment 
potassium  chromate  is  produced.  Arsenic  and 
arsenious  acid  behave  similarly.  The  same  is  true 
also  of  the  soluble  ferro-  and  ferri-cyanides  and  nitric 
acid.  In  the  presence  of  sulphuric  acid,  ferric  and 
uranic  oxides  are  reduced  to  lower  states  of  oxidation. 
Sulphates  result  in  the  electrolysis  of  the  alkaline 


HISTORICAL.  43 

sulphites,  hyposulphites  and  sulphides,  and  carbonates 
from  the  alkaline  organic  salts.  In  short,  the  current 
has  a  reducing  action  in  acid  solutions,  and  the 
opposite  effect  in  those  that  are  alkaline.  In  the 
electrolysis  of  solutions  of  hydrogen  chloride,  bromide, 
iodide,  cyanide,  ferro-  and  ferri-cyanide  and  sulphide, 
the  hydrogen  separates  at  the  electro-negative  pole, 
and  the  electro-negative  constituents  at  the  positive 
electrode.  Cyanogen  sustains  a  more  thorough  de- 
composition, the  final  products  being  carbon  dioxide 
and  ammonia.  In  the  electrolysis  of  ferro-  and  ferri- 
cyanogen,  Prussian  blue  separates  at  the  positive 
electrode.  In  dilute  chloride  solutions  hypochlorous 
acid  is  the  only  product,  whereas  chlorine  is  also 
present  in  concentrated  solutions.  In  alkaline  chloride 
solutions  chlorates  are  produced  as  soon  as  the  liquid 
becomes  alkaline.  In  the  iodides  and  bromides  iodine 
and  bromine  separate  at  the  positive  electrode,  while 
bromates  and  iodates  are  formed  when  metals  of  the 
first  two  groups  are  present.  Potassium  cyanide  is 
converted  into  potassium  and  ammonium  carbonates. 
Concentrated  nitric  acid  is  reduced  to  nitrous  acid  ; 
however,  when  its  specific  gravity  equals  1.2,  this  does 
not  occur,  at  least  not  when  a  feeble  current  is  used. 
Dilute  nitric  acid  alone,  or  even  in  the  presence  of 
sulphuric  acid,  is  not  reduced  to  ammonia.  If,  how- 
ever, dilute  nitric  acid  be  present  in  a  copper  sulphate 
solution  undergoing  electrolysis,  copper  will  separate 
upon  the  negative  electrode  and  ammonium  sulphate 


44  ELECTRO-CHEMICAL   ANALYSIS. 

will  be  formed.  Solutions  of  nitrates,  containing  .sul- 
phuric acid,  behave  analogously.  Phosphoric  acid 
sustains  no  change.  Silicic  acid  separates  as  a  white 
mass,  and  boric  acid,  in  crystals  uniting  to  arborescent 
groups,  at  the  positive  electrode. 

In  the  Ber.  d.  d.  chem.  Gesellschaft  for  1881  (Vol. 
14,  1622),  Classen  and  v.  Reiss  presented  the  first  of 
a  series  of  papers  upon  electrolytic  subjects,  which 
continued  through  subsequent  issues  of  this  publica- 
tion. Their  early  work  was  devoted  to  the  precipita- 
tion of  metals  from  solutions  of  their  double  oxalates. 
They  also  elaborated  excellent  methods  for  antimony 
and  tin.  Many  very  serviceable  forms  of  apparatus, 
intended  for  electrolytic  work,  were  devised  and  de- 
scribed by  them,  and  it  must  be  conceded  that  through 
the  activity  of  the  Aachen  School  electrolysis  acquired 
more  importance  in  the  eyes  of  the  chemical  public 
than  it  ever  before  possessed.  The  details  of  the 
more  important  methods  proposed  by  Classen  and 
his  co-laborers  will  receive  due  mention  under  the 
respective  metals. 

At  the  same  time  with  and  quite  independently  of 
Classen,  Reinhardt  and  Ihle  proposed  the  double  oxa- 
lates for  the  estimation  of  zinc  electrolytically ;  and 
in  this  connection  it  may  not  be  improper  to  mention 
that  as  early  as  1879,  two  years  prior  to  the  publica- 
tion of  Classen's  first  communication,  Parodi  and  Mas- 
cazzini  (Gazetta  chimica  italiana,  Vol.  8)  announced 
that  antimony  and  iron  could  be  deposited  completely 


HISTORICAL.  45 

and  in  compact  form  by  electrolysing  the  solutions 
of  the  sulpho-salts  of  the  former  and  the  chloride 
of  the  lattter  in  the  presence  of  acid  ammonium 
oxalate. 

In  1883,  Gibbs  recommended  placing  solutions  of 
mercury,  tin  and  cobalt  in  a  beaker  glass,  on  the 
bottom  of  which  was  placed  a  layer  of  mercury, 
which  served  as  the  negative  electrode.  Knowing 
the  combined  weight  of  the  beaker  and  mercury,  the 
increased  weight,  after  precipitation  and  removal  of 
the  liquid,  will  give  the  quantity  of  metal  under 
examination.  This  method  is  not  applicable  in  the 
case  of  antimony  and  arsenic. 

Three  years  later  (1886)  Luckow  recommended  a 
very  similar  procedure  for  the  estimation  of  zinc. 

Moore  (1886)  also  published  new  data  upon  the 
estimation  of  iron,  cobalt,  nickel,  manganese,  etc.,  full 
notice  of  which  will  appear  under  these  metals. 

The  most  recent  publications  relating  to  electrolysis 
are  those  of  Brand,  who  succeeded  in  effecting  sepa- 
rations by  utilizing  solutions  of  the  pyrophosphates  of 
different  metals,  and  those  of  Smith  and  Frankel,  who 
have  made  an  extended  study  of  the  double  cyanides, 
and  found  thereby  a  number  of  very  convenient 
methods  of  separation  heretofore  unrecorded.  The 
results  are  given  in  detail  in  the  following  pages. 

The  preceding  paragraphs  give  a  brief  outline  of 
what  has  been  accomplished  in  the  field  of  analysis  by 


46  ELECTRO-CHEMICAL   ANALYSIS. 

electrolysis ;  for  further  information  consult  the  fol- 
lowing 

LITERATURE. — Jahrb.,  1850,  602;  C.  r.,  45,  449;  Jr.  f.  pkt.  Ch.,  73, 
79;  Chem.  Soc.  Quart.  Journ.,  13,  12;  Jahrb.,  1862,  610;  Ann.,  124, 
131;  C.  r.,  55,  18;  Ann.,  146,  375;  Z.  f.  a.  Ch.,  3,  334;  Ding.  p.  Jr. 
(1865),  231  ;  Z.  f.  a.  Ch.,  8,  23;  n,  I,  9;  13,  183;  Am.  Jr.  Sc.  and 
Ar.  (3d  ser.),  6,  255;  Z.  f.  a.  Ch.,  15,  297;  Ber.,  10,  1098;  Annales 
de  Ch.  et  de  Phy.,  1878;  Am.  Jr.  Sc.  and  Ar.,  16,  200;  Am.  Phil.  Soc. 
Pr.,  1878;  Z.  f.  a.  Ch.,  15,  303;  Am.  Ch.  Jr.,  2,  41;  Berg-Hutt.  Z., 
37,  41;  Z.  f.  a.  Ch.,  19,  i,  314,  324;  Am.  Ch.  Jr.,  i,  341;  B.  s.  Ch. 
Paris,  34,  18;  Ber.,  12,  1446;  14,  1622,  2771;  17,  1611,  2467,  2931; 
18,  168,  1104,  1787;  19,  323;  21,  359,  2892,  2900;  Jr.  f.  pkt.  Ch., 
24,  193;  Z.  f.  a.  Ch.,  18,  588;  22,  558;  25,  113;  Chem.  News,  28, 
581 ;  53,  209.  And  the  following  will  be  found  worthy  of  careful 
study:  Ann.,  36,  32;  94,  i;  Z.  f.  a.  Ch.,  19,  I ;  Berg-Hutt.  Z.,  42, 
377;  Z.  f.  a.  Ch.,  22,  485. 


SPECIAL    PART. 


i.  DETERMINATION  OF  THE   DIFFER- 
ENT METALS. 

COPPER. 

LITERATURE.— Gibbs,  Z.  f.  a.  Ch.,  3,  334;  Boisbaudran,  B.  s. 
Ch.,  Paris,  1867,  p.  468;  Merrick,  Am.  Ch.,  2,  136;  Wrightson, 
Z.  f.  a  Ch.,  15,  299;  Her  pin,  Z.  f.  a.  Ch.,  15,  335  ;  Moniteur  Scien- 
tifique  [3  ser.],  5,41 ;  Ohl,  Z.  f.  a.  Ch.,  18,  523;  Classen,  Ber.,  14, 
1622,  1627  ;  Classen  and  v.  Reiss,  Z.  f.  a.  Ch.,  24,  246;  25,  113; 
Riche,  Z.  f.  a.  Ch.,  21,  116;  M  akin  tosh  ,  Am.  Ch.  Jr.,  3,  354; 
Rudorff,  Ber.,  21,  3050;  Luckow,  Z.  f.  a.  Ch.,  8,  23. 

Dissolve  19.6  grams  of  pure  copper  sulphate  in 
water,  and  dilute  to  I  litre.  Place  50  c.c.  of  this  solu- 
tion (=  0.25  gram  of  metallic  copper)  in  a  clean  plati- 
num dish,  previously  weighed.  Connect  the  dish  with 
a  battery,  whose  current  is  sufficiently  strong  to  effect 
the  complete  precipitation  of  the  copper  in  the  course 
of  ten  or  twelve  hours.  The  apparatus  may  be 
arranged  as  in  the  accompanying  sketch  (Fig.  16), 
page  48. 

A  is  an  ordinary  filter  stand,  upon  the  base  of  which 
is  fixed  a  binding-post,  x,  to  which  is  attached  a  heavy 
copper  ring  for  the  support  of  the  platinum  vessel.  It 

47 


48 


ELECTRO-CHEMICAL   ANALYSIS. 


DETERMINATION    OF    METALS COPPER.  49 

is  in  connection  with  the  negative  electrode  of  the  bat- 
tery. The  arm,  yt  has  been  shortened,  and  at  its 
extremity  there  is  a  second  binding-screw,/;  the  lat- 
ter holds  the  positive  pole  (a  heavy  platinum  wire 
bent  into  a  flat  spiral  at  its  lower  end),  and  the  copper 
wire  from  the  anode  of  the  battery  (the  copper  plate 
in  a  "  Crowfoot "  cell).  It  will  be  noticed  that  the 
current  passes  through  the  vessel,  B  (a  Bunsen  volta- 
meter), in  which  acidulated  water  is  undergoing  de- 
composition, the  resulting  gases  being  collected  in  d. 
Their  volume  serves  to  measure  the  strength  of  the 
acting  current.  Copper  is  very  readily  precipitated 
from  solutions  containing  free  nitric  or  sulphuric  acid. 
Hydrochloric  acid  should  never  be  present. 

Having  arranged  the  apparatus  as  just  described, 
add  9-10  drops  of  concentrated  nitric  acid  to  the  solu- 
tion of  the  electrolyte ;  cover  the  vessel  with  a  perfo- 
rated watch  crystal  during  the  decomposition.  To 
ascertain  when  the  metal  has  been  completely  precipi- 
tated, add  water  to  the  dish ;  this  will  expose  a  clean, 
platinum  surface,  and  if  in  the  course  of  half  an  hour 
no  copper  appears  upon  it,  the  deposition  may  be  con- 
sidered as  finished.  Or,  a  drop  of  the  liquid  may  be 
removed,  and  brought  in  contact  with  a  drop  of 
ammonium  hydroxide  or  hydrogen  sulphide,  when,  if 
a  blue  coloration  or  black  precipitate  is  not  produced, 
the  deposition  can  be  considered  ended. 

As  the  precipitation  has  been  made  in  an  acid  solu- 
tion, the  current  should  not  be  interrupted  until  the 


50  ELECTRO-CHEMICAL   ANALYSIS. 

acid  liquid  has  been  removed,  for  in  many  cases  the 
brief  period  during  which  the  acid  can  act  upon  the 
metal  will  be  sufficient  to  cause  some  of  the  latter  to 
pass  into  solution.  To  obviate  this,  siphon  off  the 

FIG  17. 


acid  liquid.  The  sketch  (Fig.  17)  shows  how  this  can 
be  done.  A  rubber  tube  of  small  diameter  may  be 
substituted  for  the  glass  siphon.  As  the  acidulated 
water  is  conveyed  away  by  the  latter,  pour  distilled 


DETERMINATION    OF   METALS COPPER.  51 

water  into  the  dish.  Empty  the  platinum  dish  twice 
in  this  way ;  the  current  can  then  be  interrupted  with- 
out loss  of  copper.  Finally,  disconnect  the  dish,  wash 
the  deposit  with  hot  water  and  then  with  alcohol.  Dry 
the  precipitated  copper  at  a  temperature  not  exceed- 
ing 1 00°  C;  an  air-batH,  an  asbestos  plate,  or  warm 
iron  plate  will  answer  for,  this  purpose.  Do  not  weigh 
the  dish  until  it  is  perfectly  cold,  and  has  attained  the 
temperature  of  the  balance-room.  • 

In  the  ordinary  precipitations  of  copper  from  dilute 
nitric  or  sulphuric  acid  solution  a  current,  giving 
0.3-0.5  c.c.  oxy-hydrogen  gas  (electrolytic  gas)  per 
minute,  will  be  amply  sufficient.  The  deposition  can 
also  be  made  in  a  platinum  crucible,  or  the  copper  can 
be  precipitated  upon  the  exterior  surface  of  the  same. 
This  is  sometimes  convenient.  Place  the  liquid  under- 
going electrolysis  in  a  beaker  glass  (capacity  100-250 
c.c.),  and  suspend  the  crucible  in  it  (Fig.  18);  support- 
ing it  there  by  a. tight-fitting  cork,  through  which 
passes  a  stout  copper  wire,  w,  in  connection  with  the 
negative  electrode  of  a  battery.  The  positive  electrode 
is  a  platinum  plate  projecting  into  the  liquid.  The  end 
of  the  decomposition  may  be  learned  by  pressing  down 
upon  w,  or  by  adding  water  to  the  solution  in  the 
beaker.  No  further  appearance  of  copper  on  the  newly 
exposed  platinum  indicates  the  end  of  the  precipita- 
tion. Raise  the  crucible  from  the  liquid,  wash  the 
copper  with  water,  then  detach  the  vessel  carefully 
from  the  cork,  and  dry  as  already  directed. 


52  ELECTRO-CHEMICAL    ANALYSIS. 

Instead  of  using  either  of  the  suggestions  first 
offered,  substitute  the  apparatus  of  Riche  (Fig.  19)  if 
convenient.  This  consists  in  suspending  a  crucible 
within  a  crucible.  The  sides  of  the  inner  vessel  are 
perforated  so  that  the  liquid  will  maintain  uniform 


FIG.  i 8. 


FIG.  19. 


concentration.    It  is  practically  the  same  as  the  device 
just  described  above. 

Copper  can  also  be  precipitated  from  the  solution  of 
ammonium-copper  oxalate.  To  this  end  the  copper 
solution  (sulphate  or  chloride)  is  treated  with  an  ex- 
cess of  a  saturated  solution  of  ammonium  oxalate, 
care  being  taken  that  the  entire  volume  does  not 


DETERMINATION    OF   METALS — COPPER. 


53 


exceed  170—200  c.c.  A  current  liberating  0.1—0.2  c.c. 
oxy-hydrogen  gas  per  minute  will  answer  for  the 
deposition,  which  will  require  about  twelve  hours.  If 
the  double  oxalate  solution  be  heated  to  70°,  and 
held  at  that  temperature,  the  decomposition  will  be 
finished  in  five  hours  at  the  most.  Use  ferrocyanide 

FIG.  20. 


of  potassium  to  learn  whether  all  the  metal  has  been 
precipitated.     Wash  and  dry  as  already  instructed. 

Riidorff  obtained  excellent  results  with  the  follow- 
ing conditions:  0.1-0.3  gram  of  metallic  copper  in  100 
c.c.  water,  to  which  were  added  2-3  grams  of  potas- 
sium or  ammonium  nitrate,  and  10  c.c.  of  ammonium 


54  ELECTRO-CHEMICAL   ANALYSIS. 

hydroxide.  A  current  giving  0.5  c.c.  oxy-hydrogen 
gas  per  minute  will  throw  out  the  copper  from  this 
solution. 

Moore  advises  dissolving  the  recently  precipitated 
copper  sulphide,  obtained  in  the  ordinary  course  of 
analysis,  in  potassium  cyanide;  and,  after  the  addition 
of  an  excess  of  ammonium  carbonate,  electrolyses  the 
warm  (70°)  solution. 

In  the  analysis  of  commercial  copper  Luckovv  em- 
ployed the  apparatus  pictured  in  Fig.  20.  The  beaker 
(a)  contains  the  electrolyte,  and. the  metal  is  precipi- 
tated upon  the  cylinder  of  platinum  (ti).  It  is  a  very 
satisfactory  device  for  almost  any  kind  of  electrolytic 
work. 

Foote  (Am.  Ch.  Jr.,  6,  333)  has  also  described  a 
very  excellent  improvement  in  the  apparatus  intended 
for  the  electrolytic  precipitation  of  copper. 


CADMIUM. 

LITERATURE. — Ber.,  11,2048;  Smith,  Am.  Phil.  Soc.  Pr.,  1878; 
Clarke,  Z.  f.  a.  Ch.,  18,  104;  Beilstein  and  Jawein,  Ber.,  12, 
759;  Smith,  Am.  Ch.  Jr.,  2,  42;  Luckow,  Z.  f.  a.  Ch.,  19,  16; 
Wright  son,  Z.  f.  a.  Ch.,  15,303;  Class  en  and  v.  Reiss,  Ber., 
14,  1628. 

Cadmium  can  be  determined  electrolytically  as 
readily  as  copper.  Prepare  a  solution  of  the  chloride 
or  sulphate  of  definite  strength.  Remove  50  c.c.  to  a 
suitable,  weighed  platinum  vessel.  Add  one  gram  of 


DETERMINATION    OF    METALS CADMIUM.  55 

pure  potassium  cyanide  ;  dilute  with  water  to  150-200 
c.c.,  and  then  connect  with  five  or  six  "  Crowfoot " 
cells  in  the  same  manner  as  directed  under  copper. 
Introduce  the  voltameter  as  there  indicated.  It  is  well 
to  commence  the  decomposition  in  the  evening,  and 
by  morning  the  metal  will  be  fully  deposited.  A 
current  yielding  0.3  c.c.  electrolytic  gas  per  minute 
will  precipitate  0.2  gram  metal  in  this  time.  To  ascer- 
tain whether  the  precipitation  is  complete,  raise  the 
level  of  the  liquid  in  the  platinum  dish.  In  washing, 
it  will  not  be  necessary  to  siphon  off  the  supernatant 
liquid ;  it  can  be  poured  off,  after  interruption  of  the 
current,  without  loss  of  metal  from  re-solution.  Wash 
the  deposit  with  cold  and  hot  water.  Dry  upon  a 
warm  iron  plate  (temperature  not  exceeding  100°  C.). 

Cadmium  may  also  be  precipitated  from  a  solution 
of  its  sulphate  containing  a  small  amount  of  free  sul- 
phuric acid  (2  c.c.  H2SO4,  sp.  gr.  1.09  for  o.i  gram 
cadmium).  When  operating  with  a  solution  of  this 
character,  use  a  current  generating  5  c.c.  electrolytic 
gas  per  minute.  Two  Bunsen  cells  will  answer, 
although  it  may  be  necessary  to  reduce  the  current  to 
some  degree ;  this  can  be  accomplished  by  introducing 
one  of  the  resistances  described  on  pages  26  and  27. 
Arrange  the  apparatus  as  under  copper.  The  pre- 
cipitation takes  place  at  the  ordinary  temperature. 

Cadmium  can  also  be  deposited  quite  readily,  and 
in  a  crystalline  form,  from  its  acetate  solution.  In 
this  case  the  liquid,  containing  an  excess  of  free  acetic 


50  ELECTRO-CHEMICAL   ANALYSIS. 

acid,  is  heated  to  70-80°  during  the  decomposition. 
The  apparatus  can  be  arranged  as  in  Fig.  21.  The 
platinum  dish  is  placed  in  a  water  bath,  and  the  current 
made  to  pass  through  R  (resistance  frame)  and  V 
(voltameter).  An  asbestos  plate  may  be  substituted 


for  the  water  bath.  The  current  should  give  I  J^-2 
c.c.  of  oxy-hydrogen  gas  per  minute.  This  will  insure 
the  precipitation  of  0.12-0.15  gram  of  cadmium  in 
five  to  six  hours.  When  the  precipitation  is  completed, 
detach  the  dish,  wash  the  deposited  metal  first  with 


DETERMINATION    OF    METALS MERCURY.  57 

warm  water,  then  with  absolute  alcohol,  and  finally 
with  ether.  Dry  upon  a  moderately  warm  plate. 

If  desired,  the  metal  can  also  be  precipitated  from 
the  solution  of  the  double  oxalate  of  ammonium  and 
cadmium  (see  Copper). 

In  the  usual  course  of  gravimetric  analysis  cad- 
mium is  obtained  as  sulphide.  To  prepare  it  for  elec- 
trolysis dissolve  the  same  in  nitric  acid,  and  after 
expelling  the  excess  of  the  latter,  add  a  small  amount 
of  potassium  hydroxide  (sufficient  to  precipitate  the 
cadmium),  and  follow  this  with  an  excess  of  potassium 
cyanide  (i  to  2  grams).  Proceed  further  as  already 
directed. 

MERCURY. 

LITERATURE. — Ber.,  6,  270;  Clarke,  Am.  Jr.  Sc.  and  Ar.,  16,  200; 
Classen  and  Ludwig,  Ber.,  19,  323;  Hoskinson,  Am.  Ch.  Jr.,  8, 
209;  Smith  and  Knerr,  ibid.;  Smith  and  Frankel,  Am.  Ch.  Jr., 
n,  264. 

In  preparing  solutions  for  experimental  purposes, 
use  either  mercuric  nitrate  or  chloride.  A  current 
equivalent  to  0.5-1.0  c.c.  electrolytic  gas  per  minute 
will  precipitate  0.3  gram  of  mercury  from  such  solu- 
tions (add  a  slight  amount  of  free  nitric  acid)  in  twelve 
hours.  The  deposit  will  be  drop-like  in  appearance. 
Even  in  the  presence  of  considerable  free  nitric  acid 
it  has  been  found  that  a  current  of  4  c.c.  electrolytic 
gas  per  minute  will  suffice  to  precipitate  as  much  as 
o.io  gram  of  metal  in  30  to  45  minutes.  In  such  cases 
E 


58  ELECTRO-CHEMICAL   ANALYSIS. 

the  acid  liquid  must  be  removed  before  the  interrup- 
tion of  the  current  occurs. 

A  mercuric  chloride  solution,  feebly  acidulated 
with  sulphuric  acid,  gradually  yields  its  metal  to 
a  current,  giving  5—6  c.  c.  oxy-hydrogen  gas  per 
minute.  Always  wash  the  deposited  metal  with  cold 
water. 

From  experiments  made  in  this  laboratory  the  writer 
prefers  and  would  especially  recommend  solutions  of 
the  double  cyanide  of  mercury  and  potassium  for  the 
electrolytic  deposition  of  mercury.  A  current  of  0.2 
c.c  electrolytic  gas  per  minute  will  precipitate  from 
0.10-0.20  gram  of  metal  in  twelve  hours.  This  pro- 
cedure requires  no  further  attention  after  it  is  once 
set  in  operation.  The  deposit  is  always  compact, 
and  gray  in  color.  Use  water  only  in  washing  it, 
for  alcohol  seems  to  detach  some  of  the  metallic 
film.  The  quantity  of  alkaline  cyanide  present  may 
vary  from  0.26-2.6  grams  (KCN)  for  every  gram  of 
mercury. 

In  general  analysis  mercury  is  frequently  obtained 
as  sulphide.  Its  determination  in  this  form  requires 
time  and  exceeding  care.  As  a  substitute  for  this  the 
writer  would  advise  the  solution  of  the  sulphide  in 
acid,  and  after  neutralizing  the  excess  of  the  latter 
with  caustic  alkali,  add  an  excess  of  pure  potassium 
cyanide,  and  electrolyse  as  above  indicated.  It  is  best 
to  use  a  platinum  dish  as  the  negative  electrode,  and 
a  platinum  spiral  (p.  49)  for  the  anode.  Dry  the 


DETERMINATION   OF    METALS BISMUTH.  59 

deposit  on  a  moderately  warm  plate,  or  over  sulphuric 
acid.  "  Crowfoot  "  cells  are  well  adapted  for  decom- 
positions of  this  kind. 


BISMUTH. 

LITERATURE. — Luckow,  Z.f.  a.  Ch.,ig,i6;  Classen  and  v.  Reiss, 
Ber.,  14,  1622;  Thomas  and  Smith,  Am.  Ch.  Jr.,  5,  114;  Moore, 
Ch.  News,  53,  209;  Smith  and  Knerr,  Am.  Ch.  Jr.,  8,  206; 
Schucht,  Z.  f.  a.  Ch.,  22,  492;  Eliasberg,  Ber.,  19,  326;  Brand, 
Z.  f.  a.  Ch.,  28,  596. 

Prepare  a  solution  of  definite  value  as  directed 
under  the  preceding  metals.  To  a  portion  of  it  add 
an  excess  of  a  cold  ammonium  oxalate  solution,  and 
act  upon  the  mixture  with  a  current  of  o.io  c.c.  oxy- 
hydrogen  gas  per  minute.  Those  who  have  employed 
this  method  find  that  the  deposit  is  not  very  adherent, 
•and  great  care  must  be  taken  to  expose  as  large  a  pla- 
tinum surface  as  possible.  If  metallic  particles  do  sepa- 
rate, collect  them  upon  a  small  filter  and  weigh  alone. 

Eliasberg  advises  bringing  the  solution  of  the  metal 
into  a  weighed  platinum  dish,  and  then  adding  10  c.c. 
of  a  potassium  oxalate  solution  (i  13).  Heat  is  applied, 
and  solid  ammonium  oxalate  is  introduced  until  com- 
plete solution  ensues.  Dilute  to  170-180  c.c.,  and 
warm  to  70-80°  C,  while  the  current  acts.  The  latter 
should  be  so  feeble  that  the  liberation  of  gas  in  the 
voltameter  is  scarcely  perceptible.  In  sixteen  hours 
the  greater  portion  of  the  metal  will  have  separated, 


60  ELECTRO-CHEMICAL   ANALYSIS. 

and  then  oxalic  acid  is  added  to  distinct  acid  reaction. 
As  soon  as  the  metal  is  fully  precipitated,  interrupt  the 
current  and  wash  the  deposit  with  water.  Take  special 
pains  in  drying,  so  that  the  metal  does  not  oxidize. 

Experiments  made  in  this  laboratory  demonstrate 
that  by  electrolysing  the  sulphate,  an  alkaline  citrate 
solution,  or  one  containing  free  citric  acid,  the  bis- 
muth will  be  rapidly  and  completely  precipitated.  In 
some  cases  the  deposits  were  made  in  small  platinum 
crucibles,  while  others  were  thrown  upon  the  exterior 
surface  of  the  crucibles  arranged  as  under  Copper.  If 
peroxide  should  separate  upon  the  anode  in  the  electro- 
lysis of  citrate  or  sulphate  solutions  of  bismuth,  it  will 
disappear  before  the  decomposition  is  fully  ended. 
Heat  is  not  required.  The  best  results  were  obtained 
with  solutions  of  the  sulphate,  containing  free  sul- 
phuric acid.  For  example:  0.1542  gram  of  bismuth, 
as  sulphate,  3  c.c.  sulphuric  acid  (1.09  sp.  gr.),  and  150 
c. c.  of  water,  required  a  current  giving  3  c.c.  oxy- 
hydrogen  gas  per  minute,  for  a  period  of  three  hours, 
to  effect  the  complete  separation  of  the  metal.  The 
latter  was  quite  compact  and  offered  no  difficulty  in 
washing  with  water  and  alcohol.  An  air-bath  was 
used  for  drying  purposes. 

Moore  recommends  the  following  method :  add 
sufficient  tartaric  acid  to  the  bismuth  solution  to 
prevent  the  precipitation  of  a  basic  salt,  then,  after 
rendering  the  solution  slightly  alkaline  with  ammon- 
ium hydroxide,  add  a  considerable  excess  of  glacial 


DETERMINATION   OF   METALS BISMUTH.  6 1 

phosphoric  acid,  so  that  the  solution  has  a  strong  acid 
reaction.  The  current  should  give  0.33-0.50  c.c. 
electrolytic  gas  per  minute,  at  first,  but  this  must  be 
increased  at  last  to  7.5  c.c.  per  minute.  The  deposit 
at  the  beginning  of  the  deposition  is  loose,  but 
gradually  becomes  hard  and  compact. 

Brand's  recommendation  consists  in  adding  to  a 
somewhat  dilute  acid  solution  of  bismuth  from  four 
to  five  times  as  much  sodium  pyrophosphate  as  will 
be  necessary  to  form  the  double  salt.  Ammonium 
carbonate  is  then  carefully  introduced  until  the  re- 
action of  the  liquid  is  distinctly  alkaline,  when  3—5 
grams  of  ammonium  oxalate  are  added.  The  total 
dilution  should  be  about  200  c.c.  The  electrolysis  is 
commenced  with  a  current  giving  o.i-i.o  c.c.  electro- 
lytic gas  per  minute,  although  toward  the  close  it  will 
be  necessary  to  increase  the  same  to  2-3  c.c.  per  min- 
ute. By  following  these  instructions  0.2500  gram  of 
bismuth  can  be  precipitated  in  twelve  hours.  When 
considerable  quantity  of  metal  is  present  in  solution  a 
feeble  current  should  be  used  at  first.  If  the  peroxide 
appears  upon  the  anode  in  the  course  of  the  decompo- 
sition, redissolve  it  in  a  few  drops  of  a  concentrated 
solution  of  oxalic  acid.  However,  this  should  not  be 
done  until  there  is  no  further  separation  of  metal  upon 
the  cathode.  The  final  reduction  is  ascertained  by 
testing  with  hydrogen  sulphide.  The  metal  is  said 
to  sustain  a  superficial  oxidation,  hence  it  is  converted 
into  oxide  and  weighed  as  such. 


62  ELECTRO-CHEMICAL   ANALYSIS. 


LEAD. 

LITERATURE. — Luckow,  Z.  f.  a.  Ch.,  19,  215;  Riche,  Ann.  de 
Chim.  et  de  Phys.  [5  ser.],  13,  508;  Z.  f.  a.  Ch.,  21,  117;  Classen, 
ibid.,  257;  Hampe,  Z.  f.  a.  Ch.,  13,  183;  May,  Am.  Jr.  Sc.  and  Ar. 
[3  ser.],  6,  255,  also  Z.  f.  a.  Ch.,  14,  347 ;  Parodi  and  Mascazzini, 
Ber.,  10,  1098 ;  Z.  f.  a.  Ch.,  16,  469;  18,588;  Riche,  Z.  f.  a.  Ch.,  17, 
219;  Schucht,  Z.  f.  a.  Ch.,  21,  488;  Tenney,  Am.  Ch.  Jr.,  5,  413; 
Smith,  Am.  Phil.  Soc.  Pr.,  24,  428. 

The  metal  may  be  obtained  by  electrolysing  so- 
lutions of  the  double  oxalate(see  Copper  and  Cadmium), 
the  acetate,  the  oxide  in  sodium  hydroxide,  or  the 
phosphate  dissolved  in  the  latter  reagent.  A  current 
of  o.  I— 0.2  c.c.  electrolytic  gas  per  minute,  is  sufficient 
for  this  purpose.  While  the  metal  separates  well  from 
either  one  of  these  solutions,  difficulty  is  experienced 
in  drying  the  deposit,  for  the  moist  metal  almost  in- 
variably suffers  a  partial  oxidation,  thus  rendering  the 
results  high.  The  deposit  can  be  dried,  without  oxid- 
ation, in  an  atmosphere  of  hydrogen,  but  for  the  in- 
experienced operator  this  procedure  offers  little  satis- 
faction. It  is,  therefore,  better  to  utilize  the  tendency 
of  lead  to  separate,  from  acid  solutions,  as  the  dioxide. 
For  trial  purposes  make  up  a  definite  volume  of  lead 
nitrate.  Electrolyse  several  portions  (=  o.i  gram  lead 
each)  in  a  platinum  dish  connected  ivith  the  anode  of  a 
battery,  giving  0.1-0.2  c.c.  electrolytic  gas  per  minute. 
In  order  that  the  lead  may  be  precipitated  wholly 
as  dioxide  upon  the  positive  electrode  and  none  in 
metallic  form  upon  the  cathode,  it  is  necessary  that 


DETERMINATION   OF   METALS —SILVER.  63 

the  solution  being  analyzed  should  contain  from  ten 
to  twenty  per  cent,  of  free  nitric  acid.  This  quantity 
of  acid  is  required  when  lead  alone  is  present  in  so- 
lution. In  the  presence  of  other  metals  the  complete 
deposition  of  the  lead  as  dioxide  occurs  with  even 
less  acid  (eight  per  cent.).  At  the  end  of  the  precipi- 
tation siphon  off  the  acid  liquid,  and  wash  in  the  dish, 
then  dry  the  deposit  at  1 10°  C,  and  weigh.  Reference 
to  the  literature  shows  that  May  preferred,  after  dry- 
ing the  deposit,  to  carefully  ignite  it  and  finally  weigh 
as  lead  oxide  (PbO).  This  deportment  of  lead  affords 
an  excellent  method  by  which  to  separate  it  from 
other  metals,  e.g.,  mercury,  copper,  cadmium,  silver, 
and  all  those  soluble  in  nitric  acid,  or  those  which,  in 
a  nitric  acid  solution,  are  deposited  upon  the  electro- 
negative pole  of  a  battery. 

The  analysis  of  an  alloy  of  lead,  bismuth  and 
copper  can  be  most  satisfactorily  made  by  employing 
electrolytic  methods  (see  Separations). 


SILVER. 

LITERATURE. — Luckow,  Ding.  p.  Jr.,  178,  43,  Z.  f.  a.  Ch.,  19, 
15;  Fresenius  and  Bergmann,  Z.  f.  a.  Ch.,  19,  324;  K  rut  wig, 
Ber.,  15,  1267;  Schucht,  Z.  f.  a.  Ch.,  22,  417;  Kinnicutt,  Am. 
Ch.  Jr.,  4,  22. 

The  experiments  of  Luckow  showed  that  this  metal 
could  be  deposited  from  solutions  containing  as  high 
as  eight  to  ten  per  cent,  ef  free  nitric  acid.  The 


64  ELECTRO-CHEMICAL   ANALYSIS. 

deposit  was  spongy,  and  there  was  a  simultaneous 
deposition  of  silver  peroxide  at  the  anode.  This  was, 
however,  prevented  by  adding  to  the  solution  some 
glycerol,  lactic  or  tartaric  acid.  A  voluminous  mass 
was  also  obtained  from  silver  solutions,  containing  an 
excess  of  ammonium  hydroxide  or  carbonate,  and  per- 
oxide appeared  at  the  same  time  upon  the  anode. 

Fresenius  and  Bergmann,  who  have  given  the  elec- 
trolysis of  acid  solutions  of  silver  particular  study, 
observed  that  the  tendency  of  the  metal  to  sponginess 
is  most  marked  when  the  electrolyte  is  concentrated, 
and  acted  upon  by  a  strong  current.  In  a  dilute 
liquid,  the  current  being  feeble,  the  deposit  was  com- 
pact and  metallic  in  appearance  (free  acid  should  be 
present).  From  neutral  solutions,  although  very 
dilute,  the  metal  is  separated  in  a  flocculent  condition 
by  the  feeblest  currents.  Therefore,  to  obtain  results 
that  would  answer  for  quantitative  analysis,  the  fol- 
lowing conditions  were  adopted :  The  total  dilution 
of  the  solution  was  200  c.c. ;  in  this  there  was  0.03 
gram— .04  gram  silver,  and  3—6  grams  of  free  nitric 
acid.  The  poles  were  separated  about  I  cm.  from 
each  other,  while  the  current  gave  100-150  c.c.  elec- 
trolytic gas  per  hour. 

In  the  experiments  of  Fresenius  and  Bergmann, 
apparatus  similar  to  that  in  Fig.  22  was  employed. 
It  has  some  decided  advantages.  Both  spiral  (a)  and 
cone  (b)  are  constructed  of  platinum.  The  metallic 
deposition,  it  will  be  understood,  occurs  upon  the 


DETERMINATION    OF    METALS — SILVER.  65 

cone,  the  sides  of  which  are  perforated,  so  that  a  uni- 
form concentration  of  liquid  is  preserved  throughout 
the  decomposition.  When  liquid  electrolytes  contain 
much  iron,  it  is  essential  that  the  oxygen  liberated 
within  the  cone  should  be  equally  distributed  over  its 
outer  surface.  This  is  made  possible  through  open- 
ings. The  shape  of  the  cone  also  prevents  loss  from 

FIG  22. 


the  bursting  of  the  bubbles,  arising  from  the  platinum 
spiral  in  connection  with  the  anode. 

Krutwig  advises  adding  a  large  excess  of  ammo- 
nium sulphate  to  the  silver  solution,  previously  made 
alkaline  with  ammonium  hydroxide,  and  employs  a 
current  giving  150  c.c.  electrolytic  gas  per  hour,  but 
after  half  an  hour  the  latter  is  increased  to  300  c.c.  of 


66  ELECTRO-CHEMICAL   ANALYSIS. 

gas  per  hour.  In  this  way,  o.i  gram  of  silver  is 
precipitated  in  two  hours. 

The  writer's  experience  has  chiefly  been  with  solu- 
tions of  silver  containing  an  excess  of  alkaline  cyanide 
(l  gram  KCN  for  0.2-0.3  gram  silver).  With  these 
peroxide  separation  does  not  occur,  and  a  very  weak 
current  will  precipitate  0.15-0.20  gram  metal  in  ten 
ho.urs  from  a  cold  solution.  The  precipitation  can 
be  made  either  in  a  platinum  dish  or  crucible  as 
cathode. 

Chlorine,  bromine  and  iodine  can  be  indirectly 
estimated  electrolyttcally  by  first  precipitating  them 
as  silver  salts,  then  dissolving  the  latter  in  potassium 
cyanide,  and  exposing  "the  resulting  solution  to  the 
action  of  a  current  from  three  to  four  "  Crowfoot " 
cells. 

Luckow  reduced  silver  chloride  by  placing  it  in  a 
platinum  dish,  serving  as  the  negative  electrode,  cov- 
ered it  with  dilute  sulphuric  or  acetic  acid,  and  allowed 
the  positive  electrode  to  project  into  the  solution. 
Four  Meidinger  cells  were  strong  enough  to  reduce 
o.i  gram  silver  chloride  in  ten  minutes.  The  deposit, 
while  spongy,  was  adherent.  It  was  washed  with 
water  and  then  thoroughly  dried  to  insure  the  absence 
of  any  acid.  (See  the  reference  to  Kinnicutt's  experi- 
ments ;  also  Prescott  and  Dunn,  Jr.  An.  Ch.,  3,  373.) 


DETERMINATION   OF   METALS ZINC.  6/ 


ZINC. 

LITERATURE. — Wrightson,  Z.  f.  a.  Ch.,  15,  303;  Parodi  and 
Mascazzini,  Ber.,  10,  1098,  Z.  f.  a.  Ch.,  18,587;  Riche,  Z.  f.  a.  Ch., 
17,  216;  Beilstein  and  Jawein,  Ber.,  12,  446,  Z.  f.  a.  Ch.,  18,  588; 
Riche,  Z.  f.  a.  Ch.,  21,  119;  Reinhardt  and  Ihle,  Jr.  f.  pkt.  Ch., 
[N.  F.],  24,  193;  Classen  and  v.  Reiss,  Ber.,  14,  1622;  Gibbs, 
Z.  f.  a.  Ch.,  22,  558;  Luckovv,  Z.  f.  a.  Ch.,  25,  113. 

Much  has  been  written  upon  the  electrolytic  esti- 
mation of  zinc.  The  personal  experience  of  the  writer 
inclines  him  to  give  preference  to  the  method  sug- 
gested by  Parodi  and  Mascazzini.  They  recommended 
that  the  metal  be  present  in  solution  as  sulphate ;  its 
quantity  may  vary  from  o.  1-0.25  gram.  To  it  add  4  c.c. 
of  a  solution  of  ammonium  acetate,  20  c.c.  citric  acid, 
and  dilute  to  200  c.c.  with  water.  The  electrodes  are 
then  introduced  into  the  liquid,  their  distance  apart 
being  not  more  than  a  few  millimetres.  The  precipi- 
tation can  be  made  in  a  beaker  glass,  using  a  weighed 
platinum  cone  (Fig.  22)  as  the  cathode.  The  current 
for  this  purpose  should  give  250-300  c.c.  electrolytic 
gas  per  hour.  When  the  precipitation  of  metal  has 
ended,  which  may  be  ascertained  by  removing  a  small 
quantity  of  the  liquid  with  a  capillary  tube  and  bring- 
ing it  in  contact  with  a  drop  of  a  solution  of  potassium 
ferrocyanide,  remove  the  bulk  of  the  liquid  with  a 
siphon.  Wash  the  deposit  with  water  and  alcohol. 
There  is  no  danger  of  oxidation  during  the  drying 
process.  It  will  be  discovered  on  dissolving  the  pre- 
cipitated zinc  that  a  considerable  quantity  of  the  metal 


68  ELECTRO- CHEMICAL   ANALYSIS. 

remains  unattacked,  but  this  can  be  removed  by  gently 
heating  the  residue  with  air  contact,  then  fusing  it 
with  potassium  bisulphate. 

Beilstein  and  Jawein  add  sodium  hydroxide  to  the 
solutions  of  zinc  nitrate  or  sulphate,  until  a  precipitate 
is  produced,  and  dissolve  it  in  potassium  cyanide. 
The  decomposition  is  carried  out  in  a  rather  large 
beaker  glass,  the  cathode  being  either  the  platinum 
cone  already  described  (p.  65),  or  a  rather  large  plati- 
num crucible  suspended  from  a  cork  (p.  52),  perforated 
by  a  copper  wire,  touching  the  inner  surface  of  the 
crucible.  Four  Bunsen  cells  (usual  size)  are  sufficient 
for  the  precipitation.  Wash  the  deposit  as  instructed 
above. 

Reinhardt  and  Ihle  have  objected  to  nearly  all  the 
methods  which  have  been  proposed  for  the  electrolytic 
estimation  of  zinc.  They  say  of  the  Beilstein  and 
Jawein  method  ....  that  the  results  are  fairly  good, 
....  but  a  strong  current  is  necessary,  otherwise  the 
precipitation  of  the  zinc  is  slow  and  incomplete,  .... 
the  positive  pole  diminishes  in  weight  very  appreciably, 
....  finally,  working  with  potassium  cyanide  is  very 
unpleasant.  The  writer's  experience  has  proved  that 
a  current  considerably  less  than  that  which  Beilstein 
and  Jawein  first  recommended  will  throw  out  all  the  zinc 
in  the  course  of  a  night,  and  further  that  the  anode 
is  not  appreciably  affected.  The  method  suggested 
by  Reinhardt  and  Ihle  is,  however,  very  excellent 
and  deserves  trial  by  all  interested  in  the  electrolytic 


DETERMINATION   OF   METALS  -  ZINC.  69 

estimation  of  zinc.  Its  essential  features,  taken  from 
their  publication,  are  these:  Mix  the  solution  of 
zinc  sulphate  or  chloride,  neutral  as  possible,  with  an 
excess  of  neutral  potassium  oxalate,  until  the  pre- 
cipitate, which  appears  at  first,  redissolves.  A  current 
giving  90  c.c.  electrolytic  gas  per  hour  will  answer  for 
complete  precipitation. 

The  immediate  decomposition  of  the  zinc  oxalate 
is  into  zinc  and  carbon  dioxide  (two  molecules),  and 
the  potassium  oxalate  into  carbon  dioxide  (two  mole- 
cules) and  potassium  ;  the  latter  then  reacts  with  the 
water,  so  that  while  an  abundant  liberation  of  hydrogen 
occurs  at  the  cathode,  the  alkali  simultaneously  set 
free  is  converted  into  acid  potassium  carbonate  by  the 
carbon  dioxide  at  the  anode  :  — 


K2C204  =  (Zn  +  ^KOU  +  H2)  +  4CO2. 
Cathode.  Anode. 


Therefore,  just  as  long  as  zinc  oxalate  is  being 
decomposed,  considerable  evolution  of  gas  is  notice- 
able at  the  positive  electrode,  and  when  this  dimin- 
ishes, and  occasional  bubbles  escape,  the  decomposi- 
tion is  complete,  and  the  deposition  of  metal  may  be 
considered  finished. 

Free  oxalic  acid,  or  any  other  acid,  is  not  injurious 
if  there  is  a  sufficient  quantity  of  potassium  oxalate 
present.  Nitric  acid,  however,  free  or  combined,  should 


70  ELECTRO-CHEMICAL   ANALYSIS. 

be  avoided  ;  it  gives  rise  to  ammonium  salts,  which 
prevent  the  zinc  from  separating  in  a  dense  form.  The 
acid  potassium  carbonate  produced  during  the  decom- 
position offers  great  resistance  to  the  current  ;  it  is, 
therefore,  advisable  to  add  potassium  sulphate  to  the 
solution  to  increase  its  conductivity.  Reinhardt  and 
Ihle  recommend  the  following  solutions  for  use  in 
decompositions  like  that  just  described:  166  grams  of 
potassium  oxalate  in  I  litre  of  water;  250  grams  of 
potassium  sulphate  in  I  litre  of  water,  and  a  solution 
of  oxalic  acid  saturated  at  15°  C. 

Experiments,  —  (i)  40  c.c.  of  a  solution  of  zinc  sul- 
phate (=  0.181  2  gram  metallic  zinc),  to  which  were 
added  50  c.c.  of  potassium  oxalate  and  100  c.c.  of 
potassium  sulphate,  were  electrolysed  with  a  current 
giving  109  c.c.  of  electrolytic  gas  per  hour.  After 
five  hours  the  current  was  interrupted.  The  precipi- 
tated zinc  weighed  0.1814  gram.  (2)  2.1867  grams 
brass  (containing  tin,  copper,  lead  and  zinc)  were  dis- 
solved in  nitric  acid  and  the  tin  determined  in  the 
usual  gravimetric  way.  Its  quantity  was  found  to  be 
0.04  per  cent.  In  the  filtrate,  containing  nitric  acid, 
lead  and  copper  were  determined  simultaneously  by 
electrolysis  (the  copper  separated  upon  the  cathode 
and  the  lead  as  dioxide  upon  the  anode)  :  — 


Found  /«-°-85#  Pb  and  64.60  #  Cu. 
1  \  £—0.85  «    »     •«     64.62  «     « 

The  acid  liquid  was  siphoned  off  from  the  deposits, 


DETERMINATION    OF    METALS ZINC.  /I 

evaporated  to  dryness  with  sulphuric  acid,  neutral- 
ized with  caustic  potash,  and  then  to  this  (100  c.c.  in 
volume)  solution  were  added  50  c.  c.  of  a  solution 
of  potassium  oxalate  and  100  c.  c.  of  a  solution  of 
potassium  sulphate.  The  zinc  found  equaled  34.50 
per  cent. 

When  using  this  method  employ  a  stout  platinum 
wire,  wound  to  a  spiral  at  the  one  end,  for  the  anode, 
and  a  platinum  cone  for  the  cathode.  To  avoid  the 
peculiar  spots  which  electrolytic  zinc  shows  upon  a 
platinum  surface,  it  will  be  best  to  first  coat  the  nega- 
tive electrode  with  copper  (5  grams).  In  dissolving 
the  precipitated  zinc,  use  rather  dilute  nitric  acid. 
The  copper  layer  will  be  but  slightly  attacked,  and 
after  washing  and  drying  will  serve  for  further  depo- 
sitions. Wash  the  zinc  deposit  with  water,  alcohol 
and  ether ;  dry  in  a  desiccator.  Oxidation  is  liable  to 
occur  if  an  air  bath  be  used  for  the  drying. 

Riche  employs  "  a  solution  of  the  acetate  with  an 
excess  of  ammonium  acetate,  obtained  by  supersatu- 
ration  with  ammonia,  and  acidifying  with  acetic  acid." 
This  method  affords  good  results,  as  may  be  seen 
from  the  following  determination  :  0.4736  gram  of  zinc 
sulphate  was  dissolved  in  200  c.c.  of  water,  to  which 
were  added  three  grams  of  sodium  acetate  and  ten 
drops  of  ordinary  acetic  acid.  The  current  gave  3  c.c. 
of  electrolytic  gas  per  minute.  After  two  hours  o.  1063 
gram  of  metallic  zinc  was  obtained,  the  required 
quantity  being  0.1072  gram. 


72  ELECTRO-CHEMICAL   ANALYSIS. 

Moore  seems  to  have  obtained  exceedingly  satis- 
factory results  by  precipitating  a  solution  of  zinc 
sulphate  with  sodic  phosphate,  then  adding  an  excess 
of  ammonium  carbonate,  and  after  dissolving  the  pre- 
cipitate in  potassium  cyanide,  the  solution  was  elec- 
trolysed at  a  temperature  of  80°  with  a  current  giving 
rooo  c.c.  electrolytic  gas  per  hour.  The  metal  was 
deposited  upon  a  silver-plated  electrode. 

A  very  convenient  stand  for  electrolytic  work  and 
suitable  in  the  zinc  depositions  has  been  described  by 
v.  Malapert  (Z.  f.  a.  Ch.,  26,  56),  and  since  conve- 
niently modified  by  Herrick  (Jr.  An.  Ch.,  2,  167). 


NICKEL  AND  COBALT. 

LITERATURE.— Gibbs,  Z.  f.  a.  Ch.,  3,  336;  Z.  f.  a.  Ch.,n,  10;  22, 
558;  Merrick,  Am  Ch.,  2,  136;  Wrightson,  Z.  f.  a.  Ch.,  15,  300, 
303>3335  Schweder,  Z.  f.  a.  Ch.,  16,344;  Cheney  and  Richards, 
Am.  Jr.  Sc.  and  Ar.  [3],  14,  178;  Ohl,  Z.  f.  a.  Ch.,  18,  523;  Luckow, 
Z.  f.  a.  Ch.,  19,  16;  Bergmann  and  Fresenius,  Z.  f.  a.  Ch.,  19, 
314;  Riche,  Z.  f.  a.  Ch.,  21,  116,  119;  Classen  and  v.  Reis,  Ber., 
14,1622,2771;  Schucht,  Z.  f.  a.  Ch.,  21,  493;  Kohn  and  Wood- 
gate,  Jour.  Soc.  Chem.  Industry,  8,  256. 

These  metals  are  precipitated  from  solutions  of  their 
double  cyanides,  double  oxalates,  and  sulphates  mixed 
with  alkaline  acetates,  tartrates  and  citrates,  or  from 
ammoniacal  solutions.  The  latter  seem  best  adapted 
for  nickel  depositions,  the  presence  of  ammonium 
sulphate  or  sodium  phosphate  being  favorable  to  the 
precipitation. 


DETERMINATION  OF  METALS NICKEL,  COBALT.      73 

Fresenius  and  Bergmann,  who  have  carried  out  a 
series  of  experiments  with  nickel  and  cobalt,  give  the 
following  as  satisfactory  conditions :  50  c.c.  nickel 
solution  (=0.1233  gram  nickel),  100  c.c.  ammonia 
(sp.  gr.  0.96),  io  c.c.  ammonium  sulphate  (305  grams 
of  the  salt  in  I  litre  of  water),  100  c.c.  of  water;  sepa- 

FIG.  23. 


ration  of  the  electrodes  j£~~X  cm. :  time,  four  hours. 
Current,  300  c.c.  electrolytic  gas  per  hour.  The  nickel 
found  was  0.1233  gram.  Apparatus  suitable  for  the 
decomposition  just  described  is  represented  in  Fig. 
23.  The  metal  is  deposited  upon  the  weighed  plat- 
inum cone  in  the  beaker  glass,  C.  The  vessel  is  covered 

F 


74  ELECTRO-CHEMICAL   ANALYSIS. 

with  a  glass  lid  having  suitable  apertures  for  the  posi- 
tive and  negative  electrodes.  As  soon  as  the  blue- 
colored  liquid  becomes  colorless,  an  indication  that 
the  metal  is  completely  precipitated,  remove  a  few 
drops  and  test  with  a  solution  of  potassium  sulpho- 
carbonate.  If  the  latter  causes  only  a  faint  rose-red 
coloration  the  deposition  of  metal  may  be  considered 
complete.  It  is  not  advisable  to  interrupt  the  current 
or  to  remove  the  cone  from  the  electrolysed  liquid 
until  the  latter  has  been  replaced  by  water.  This  is 
effected  by  the  vessels  to  the  left  of  the  figure :  A 
is  an  aspirator,  filled  with  water ;  B  is  air-tight  and 
empty;  x  is  a  doubly  bent  tube  extending  to  the 
bottom  of  C.  Open  p  and  the  liquid  in  C  is  gradually 
transferred  to  B.  Add  fresh  water  in  C.  Ammonium 
chloride  should  not  be  present  in  the  solution  under- 
going electrolysis. 

The  statements  upon  nickel  also  apply  to  cobalt. 
An  experiment,  taken  from  the  article  of  Fresenius 
and  Bergmann  is  here  given  as  a  guide  in  determin- 
ing cobalt:  50  c.c.  of  cobalt  sulphate  (—  0.1286  gram 
cobalt),  100  c.c.  of  ammonia,  10  c.c.  of  ammonium  sul- 
phate, 100  c.c.  water;  current,  300  c.c.  electrolytic  gas 
per  hour ;  separation  of  electrodes,  ^-^  cm.  •  Time, 
five  hours.  The  deposited  cobalt  weighed  0.1286 
gram. 

Use  potassium  sulpho-carbonate  to  test  when  the 
metal  is  fully  reduced ;  it  gives  a  wine-yellow  colora- 
tion with  even  the  most  dilute  solutions  of  cobalt  salts. 


DETERMINATION    OF    METALS — MANGANESE.          75 

When  too  little  ammonia  is  present  in  the  electro- 
lyte the  results  are  bad ;  too  much  of  this  reagent 
retards  the  deposition  of  the  cobalt. 

When  precipitating  these  metals  from  the  solutions 
of  their  double  oxalates,  the  conditions  should  be 
similar  to  those  indicated  under  Iron  (p.  78). 

The  writer  has  electrolysed  cobalt  compounds  con- 
taining an  excess  of  an  alkaline  acetate  (see  Zinc)  with 
perfectly  satisfactory  results,  and  would  recommend 
such  solutions  for  this  particular  metal. 


MANGANESE. 

LITERATURE. — Z.  f.  a.  Ch.,  ix,  14;  Rich 6,  Ann.  de  Chim.  et  de 
Phys.  [5th  sen],  13,  508;  Lu  cko  w,  Z.  f.  a.  Ch.,  19,  17  ;  Schucht, 
Z.  f.  a.  Ch.,  22,493;  Classen  and  v.  Reiss,  Ber.,  14, 1622;  Moore, 
Ch.  News,  53,  209 ;  Smith  and  Fran kel,  Jr.  An.  Ch.,  3,  385;  Ch. 
News,  60,  262;  Brand,  Z.  f.  a.  Ch.,  28,  581. 

The  electric  current  causes  this  metal,  when  in  solu- 
tion as  chloride,  nitrate  or  sulphate,  to  separate  as  the 
dioxide  upon  the  anode  (see  Lead).  In  a  solution  of 
nitric  acid,  the  hydrogen  set  free  reduces  the  acid  to 
oxides  of  nitrogen  and,  finally,  to  ammonia.  Hence, 
when  the  liquid  becomes  alkaline  or  only  slightly  acid, 
peroxide  will  also  separate  upon  the  cathode ;  it  will 
be  necessary  to  remove  this  by  means  of  a  strip  of 
paper,  and  ignite  the  same  along  with  the  greater  bulk 
of  dioxide,  weighing  all  finally  as  Mn3O4.  As  long 
as  manganese  alone  is  present  in  the  solution,  this 


76  ELECTRO-CHEMICAL   ANALYSIS. 

separation  at  both  electrodes  will  not  cause  a  serious 
result;  but  in  electrolysing  a  nitric  acid  solution  con- 
taining manganese,  magnesium  or  aluminium,  the  re- 
sults will  be  high.  For  this  reason  a  solution  of  the 
sulphate,  slightly  acidulated  with  two  to  six  drops  of 
sulphuric  acid,  is  preferable  for  electrolytic  purposes. 
Riche  advises  connecting  a  platinum  crucible  or  dish 
with  the  anode  of  a  battery,  warming  the  solution, 
during  the  deposition,  upon  a  water-bath  (7O°-9O°), 
and  then  electrolyses  with  a  current  generating 
3  c.c.  of  oxy-hydrogen  gas  per  minute.  Arrange 
the  apparatus  as  directed  under  Cadmium.  As 
soon  as  the  manganese  has  been  fully  precipitated 
as  dioxide,  the  current  is  interrupted,  the  deposit 
washed  with  water,  and  should  any  of  the  dioxide 
become  detached,  it  must  be  caught  upon  a  small 
filter,  then  dried,  ignited  and  weighed,  together  with 
the  adherent  dioxide,  which  is  changed  to  Mn3O4 
before  weighing.  In  the  presence  of  large  quantities 
of  iron,  this  precipitation  is  unsatisfactory ;  therefore, 
first  remove  the  iron  with  barium  carbonate.  Tartaric, 
oxalic  and  lactic  acids  retard  the  formation  of  manga- 
nese dioxide.  The  same  is  true  of  phosphoric  acid. 
Potassium  sulphocyanide  also  prevents  its  formation, 
and,  if  added  to  solutions  in  which  dioxide  is  already 
precipitated,  it  causes  the  same  to  redissolve. 

The  apparatus  devised  by  Herpin  (Fig.  24)  can  be 
well  applied  in  the  decomposition  of  manganese  salts. 
It  consists  of  a  platinum  dish,  A,  resting  upon  a  tripod, 


DETERMINATION   OF    METALS MANGANESE. 


77 


B,  in  connection  with  the  cathode  of  a  battery.  The 
upper  portion  of  the  dish  is  so  constructed  that  it 
will  support  an  inverted  glass  funnel,  D.  Any  loss 
from  the  bursting  of  bubbles  is  prevented  by  this 

FIG.  24. 


means.  The  anode  is  a  platinum  spiral  C.  In  esti- 
mating manganese  it  must  not  be  forgotten  to  connect 
the  dish  with  the  anode  of  the  battery  employed  for 
the  decomposition. 


78  ELECTRO-CHEMICAL   ANALYSIS. 


IRON. 

LITERATURE. — Wrightson,  Z.  f.  a.  Ch.,  15,  305;  Parodi  and 
Mascazzinl,  G.  Ch.  ital.,  8;  also  Z  f.  a.  Ch.,  18,  588;  Luckow,  Z. 
f.  a.  Ch.,  19,  18;  Classen  and  v.  Reiss,  Ber.,  14,  1622;  Moore, 
Ch.  News,  53,  209;  Smith,  Am.  Ch.  Jr.,  10,  330;  Brand,  Z.  f.  a. 
Chem.,  28,  581. 

In  the  historical  sketch  p.  44,  it  was  mentioned 
that  Parodi  and  Mascazzini  found  that  iron  could  be 
precipitated  from  solutions  of  its  double  oxalates. 
This  suggestion  has  since  been  greatly  elaborated  by 
Classen,  and  by  him  applied  to  many  other  metals. 
Following  the  recommendation  of  this  chemist  the 
iron  salt  is  placed  in  a  weighed  platinum  dish  con- 
nected with  the  cathode  of  a  battery,  and  to  this  are 
added  1  —  3  c.  c.  of  a  solution  of  potassium  oxalate 
(i  13),  and  25  c.  c.  of  water.  3-4  grams  of  ammo- 
nium oxalate  are  next  introduced  into  this  liquid  and 
dissolved  by  the  aid  of  heat,  and  the  entire  solution 
then  diluted  to  200  c.  c.,  and  electrolysed  with  a  cur- 
rent generating  12  c.  c.  of  electrolytic  gas  per  minute. 
It  is  necessary  to  increase  this  toward  the  end  of  the 
reduction,  to  insure  the  complete  deposition  of  the 
metal.  Test  the  clear  liquid,  acidulated  with  hydro- 
chloric acid,  with  potassium  sulphocyanide.  The 
solution  should  be  hot  (70°)  during  the  decomposi- 
tion. The  deposited  iron  has  a  steel-gray  color;  it 
should  be  washed  with  water,  alcohol  and  ether. 
Avoid  the  presence  of  chlorides  and  nitrates.  By 


DETERMINATION    OF    METALS IRON.  79 

carefully  complying  with  the  conditions  recommended 
by  Classen  good  results  are  sure  to  follow.  To  show 
that  persons  with  but  little  experience  can  obtain 
satisfactory  results  the  two  following  determinations, 
made  by  a  student,  are  given :  A  quantity  of  ferric 
ammonium  sulphate  (=  0.0814  gram  iron)  was  dis- 
solved in  200  c.  c.  'of  water,  and  to  this  were  added 
eight  grams  of  ammonium  oxalate.  The  solution 
was  heated  to  80°,  and  in  two  hours,  with  a  current 
of  15  c.  c.  electrolytic  gas  per  minute,  0.0814  gram 
of  iron  was  obtained.  In  a  second  experiment,  the 
quantity  of  iron  was  doubled  •(=  0.1628  gram  iron), 
while  the  ammonium  oxalate  was  1 1  grams,  tempera- 
ture 66°  and  the  current  10  c.  c.  electrolytic  gas  per 
minute.  The  precipitated  iron  weighed  0.1619  gram 
instead  of  0.1628. 

The  writer  found  the  following  procedure  admirably 
suited  for  iron  determinations:  10  c. c.  iron  solution 
(—  0.0300  gram  metal),  20  c.  c.  sodium  citrate  (28 
grams  in  %  litre)  with  a  little  free  citric  acid,  then  diluted 
with  water  to  150  c.  c.  Current,  12  c.  c.  electrolytic 
gas  per  minute.  In  four  hours  0.0303  gram  iron  was 
precipitated  from  the  cold  solution.  The  deposit  was 
washed  as  already  directed.  In  several  determina- 
tions aluminium  and  titanium  were  present  with  the 
iron,  but  the  latter  was  precipitated  free  from  the  other 
two. 

A  third  method,  originated  by  Moore,  advises  that 
glacial  phosphoric  acid  (15%  acid)  be  added  to  the 


8O  ELECTRO-CHEMICAL   ANALYSIS. 

distinctly  acid  solution  of  ferric  chloride  or  sulphate, 
until  the  yellow  color  fully  disappears,  then  a  large 
excess  of  ammonium  carbonate  added  and  gently 
warmed  until  the  liquid  becomes  clear.  On  electrolys- 
ing the  hot  (70°)  solution  by  a  current  equal  to  1200 
c.  c.  electrolytic  gas  per  hour,  the  iron  is  rapidly  and 
completely  deposited  at  the  rate  of  0.75  gram  per  hour. 
The  end  of  the  decomposition  is  recognized  by  test- 
ing a  portion  of  the  solution  with  ammonium  sulphide. 
Wash  the  deposit  as  already  directed. 


URANIUM. 

LITERATURE. — Luckow,  Z.  f.  a.  Ch.,  19,  18;  Smith,  Am.  Ch. 
Jr.,  i,  329- 

For  electrolytic  purposes  use  the  acetate  or  any  of 
the  salts  to  which  an  alkaline  acetate  has  been  added 
in  large  excess,  together  with  a  few  drops  of  free  acetic 
acid.  The  dish  in  which  the  deposition  is  made  is 
placed  upon  a  water-bath,  and  connected  with  the 
negative  electrode  of  a  battery  giving  2-3  c.c.  of  elec- 
trolytic gas  per  minute  (see  Cadmium).  Heat  the 
liquid  to  70°  throughout  the  entire  decomposition. 
The  uranium  separates  as  yellow  uranic  hydroxide 
upon  the  cathode;  by  the  continued  action  of  the 
current  it  changes  to  the  black  hydrated  protosesqui- 
oxide.  As  soon  as  the  solution  becomes  colorless, 
interrupt  the  current,  and  quickly  pour  the  clear  liquid 
upon  a  small  filter,  to  catch  any  detached  particles  of 


DETERMINATION    OF    METALS THALLIUM.  8 1 

oxide.  Wash  with  a  little  acetic  acid  and  boiling 
water ;  dry,  ignite  and  weigh  as  Ur3O4(UrsO8).  This 
method  affords  an  excellent  separation  of  uranium  from 
the  alkali  and  alkaline  earth  metals. 


THALLIUM. 

LITERATURE. — Schu  cht,  Z.  f.  a.  Ch., 22,  241,  490;  Neumann , 
Ber.,  21,  356. 

This  metal  separates  as  sesquioxide,  from  acid  solu- 
tions, upon  the  anode,  while  from  ammoniacal  liquids  it 
is  deposited  partly  as  metal  and  partly  as  oxide.  From 
oxalate  solutions,  and  from  its  double  cyanides  it  sepa- 
rates only  as  metal,  when  the  current  is  feeble.  How- 
ever, difficulty  is  experienced  in  drying  the  deposit 
without  having  it  oxidized.  In  this  respect  it  is  even 
more  troublesome  than  lead.  Neumann  utilizes  the 
current  to  separate  the  metal,  dissolves  the  latter  in 
acid  and  measures  the  liberated  hydrogen ;  from  its 
volume  he  calculates  the  quantity  of  thallium  origi- 
nally present.  For  suitable  apparatus  to  carry  out 
this  method,  consult  the  literature  cited  above. 


82  ELECTRO-CHEMICAL   ANALYSIS. 


PLATINUM,  PALLADIUM,  MOLYBDENUM, 
GOLD,  ETC. 

LITERATURE. — Luckow,  Z.  f.  a.  Ch.,  19,  13;  Classen,  Ber.,  17, 
2467;  Schucht,  Z.  f.  a.  Ch.,  22,  242;  Smith,  Am.  Ch.  Jr.,  i,  329; 
Hoskinson  and  Smith,  ibid.,  1,90;  Smith  and  Keller,  Am. 
Ch.  Jr.,  12,  252. 

The  solutions  of  platinum  salts,  slightly  acidulated 
with  sulphuric  acid,  and  acted  upon  by  a  feeble  cur- 
rent, give  up  the  metal  as  a  bright,  dense  deposit  upon 
the  dish,  frequently  so  light  as  to  be  scarcely  dis- 
tinguished from  the  latter.  In  using  platinum  vessels 
for  this  purpose,  first  coat  them  with  a  rather  thick 
layer  of  copper,  upon  which  afterward  deposit  the 
metal.  Wash  the  deposit  with  water  and  alcohol. 

In  ordinary  gravimetric  analysis,  potassium  is 
frequently  estimated  as  potassio-platinum  chloride, 
K2PtCl6.  This  operation  requires  time  and  care. 
Rather  dissolve  the  double  salt  in  water,  slightly  acidu- 
late the  solution  with  sulphuric  acid,  and  electrolyse 
with  one  Bunsen  cell.  The  deposit  will  be  black 
and  spongy  if  the  current  is  too  strong.  From  the 
quantity  of  platinum  found  calculate  the  potassium. 

The  following  facts  have  been  taken  from  Classen's 
article  (see  Literature) :  A  platinic  chloride  solution, 
containing  0.6  gram  platinum,  was  diluted  to  200  c.c. 
with  water  and  electrolysed.  In  five  hours  0.4581 
gram  platinum  had  separated.  When  mixed  with 
ammonium  oxalate  0.0996  gram  platinum  was  pre- 


DETERMINATION    OF   METALS PALLADIUM.  83 

cipitated  in  two  hours.  From  a  solution,  feebly  acidu- 
lated with  hydrochloric  acid,  four  Meidinger  cells 
precipitated  0.737  gram  platinum  in  the  course  of 
twenty-four  hours.  On  dissolving  0.5  gram  ammonio- 
platinum  chloride  in  100  c.c.  water  and  mixing  with 
ammonium  oxalate  the  current  from  one  Bunsen  cell 
precipitated  0.208  gram  platinum  in  five  hours.  0.6042 
gram  potassio-platinum  chloride  was  dissolved  in  150 
c.c.  of  water,  acidulated  with  thirty  drops  of  dilute  sul- 
phuric acid  (i  :  6),  and  in  six  hours  gave  0.2017  gram 
platinum  to  the  action  of  the  current;  0.5015  gram 
of  the  same  salt  gave  0.0956  gram  metal  in  two 
hours;  while  0.4545  gram  of  the  double  chloride 
dissolved  in  100  c.  c.  water,  and  not  acidulated,  gave 
0.0688  gram  platinum  in  three  hours. 

PALLADIUM  can  be  deposited  in  the  same  manner  as 
platinum.  The  use  of  a  feeble  current  gives  a  bright 
metallic  deposit ;  otherwise  it  is  spongy. 

It  has  been  recently  discovered,  in  this  laboratory, 
that  this  metal  can  be  rapidly  and  fully  precipitated 
from  ammoniacal  solutions  of  palladammonium  chlo- 
ride, by  a  current  liberating  0.7  c.c.  electrolytic  gas  per 
minute.  Palladammonium  chloride,  Pd(NH3Cl)2,  is 
prepared  by  adding  hydrochloric  acid  to  an  ammonium 
hydroxide  solution  of  palladious  chloride.  To  show 
the  accuracy  of  this  method  several  actual  determina- 
tions are  here  introduced:  (i)  A  quantity  of  the 
double  salt  (=  0.2228  gram  palladium)  was  dissolved 


84  ELECTRO-CHEMICAL  ANALYSIS. 

in  ammonium  hydroxide;  to  this  solution  were  added 
20-30  c.c.  of  the  same  reagent  (sp.  gr.  0.935),  and  100 
c.c.  of  water.  A  current,  giving  0.9  c.c.  electrolytic 
gas  per  minute,  acted  upon  this  mixture  through  the 
night,  and  deposited  0.2225  gram  palladium.  (2)  In 
another  experiment,  with  conditions  similar  to  those 
just  mentioned,  excepting  that  the  quantity  of  the 
palladammonium  chloride  was  doubled,  and  the  current 
reduced  to  0.7  c.c.  electrolytic  gas  per  minute,  the 
quantity  of  metal  precipitated  equaled  0.4462  gram 
instead  of  0.4456.  Oxide  did  not  separate  upon  the 
anode.  The  deposit,  when  dry,  showed  the  same 
appearance  as  is  ordinarily  observed  with  this  metal 
in  sheet  form.  It  was  washed  with  hot  (70°)  water, 
and  dried  in  an  air-bath  at  no°-ii5°.  It  is  best  to 
deposit  the  palladium  in  platinum  dishes  previously 
coated  with  silver. 

WHEN  the  electric  current  acts  upon  ammoniacal, 
or  feebly  acid  solutions  of  ammonium  molybdate,  a 
beautiful  iridescence  appears ;  as  the  action  continues 
this  assumes  a  black  color,  and  the  deposit  becomes 
more  dense.  It  is  the  hydrated  sesquioxide,  which  is 
precipitated ;  after  washing  with  hot  water  it  is  dried, 
carefully  ignited  to  molybdic  acid,  and  weighed.  The 
precipitation  can  take  place  in  a  platinum  crucible,  in 
connection  with  the  cathode  of  a  battery  liberating 
3-4  c.c.  of  electrolytic  gas  per  minute.  The  tempera- 
ture of  the  solution  should  not  fall  below  70°  ;  its 


DETERMINATION    OF    METALS TIN.  85 

volume  may  vary  from  25  c.c.-i25  c.c.  Three  hours 
were  required  for  the  precipitation  of  0.0329-0.1000 
gram  of  oxide. 

GOLD  is  best  deposited  from  solutions  of  its  double 
cyanides. 

THE  facts  relating  to  the  electrolytic  behavior  of 
vanadium,  tungsten  and  osmium  are,  at  the  present 
writing,  few  in  number  and  will  not  be  given  here. 


TIN. 

LITERATURE. — Luckow,  Z.  f.  a.  Ch.,  19,  13;  Classen  and  v. 
Reiss,  Ber.,  14,  1622;  Gibbs,  Ch.  News,  42,  291  ;  Classen,  Ber., 
!7,  2467;  18,  1104. 

Tin  may  be  deposited  either  from  a  solution  of  its 
chloride,  or  from  that  of  ammonium  tin  oxalate.  It 
is  advisable  not  to  use  potassium  oxalate  in  the  electro- 
lysis, for  then  a  basic  salt  is  liable  to  separate  upon  the 
anode.  Three  to  four  grams  of  ammonium  oxalate 
will  be  sufficient  for  the  decomposition.  The  current 
should  liberate  3  c.c.  electrolytic  gas  per  minute. 
When  electrolysing  acid  tin  solutions  do  not  interrupt 
the  current  until  the  free  acid  is  first  removed ;  this  is 
not  necessary  when  operating  with  oxalate  solutions. 

Classen  has  published  a  great  deal  of  very  valuable 
information  upon  the  electrolysis  of  this  metal,  and 
has  discovered  that  a  tin  solution,  containing  an  excess 


86  ELECTRO-CHEMICAL   ANALYSIS. 

of  ammonium  sulphide,  largely  diluted  with  water, 
yields  a  quantitative  deposition  of  the  metal  when 
exposed  to  the  action  of  a  current  from  two  Bunsen 
cells.  In  dilute  sodium  or  potassium  sulphide  solu- 
tion the  tin  precipitation  is  incomplete,  and  whenever 
such  conditions  exist,  the  sodium  or  potassium  salt 
must  be  converted  into  ammonium  sulphide.  To  this 
end  the  liquid  is  mixed  with  about  25  grams  of  ammo- 
nium sulphate,  free  from  iron,  and  the  solution  then 
carefully  warmed  in  a  covered  vessel  until  the  evolu- 
tion of  hydrogen  sulphide  ceases ;  after  which  the 
liquid  is  heated  to  incipient  ebullition  for  fifteen  min- 
utes. Allow  it  to  cool,  dissolve  any  sodium  sulphate 
which  may  have  separated  by  the  addition  of  water, 
and  electrolyse  with  a  current  of  9-10  c.c.  oxy-hydro- 
gen  gas  per  minute.  The  tin  separates  in  a  gray,  dense 
layer.  Wash  it  with  water  and  alcohol.  At  times 
sulphur  sets  itself  upon  the  tin  deposit ;  this  is  diffi- 
cult to  remove,  but  can  be  detached,  after  washing  the 
deposit  with  alcohol,  by  gently  applying  a  linen  hand- 
kerchief. 


DETERMINATION   OF    METALS ANTIMONY. 


ANTIMONY. 

LITERATURE. — Wright  son,  Z.  f.  a.  Ch.,  15,  300 ;  Parodi  and 
Mascazzini,  Z.  f.  a.  Ch.,  18,  588;  Luckow,  Z.  f.  a.  Ch.,  19,  13  ; 
Classen  and  v.  Reiss,  Ber.,  14,  1622;  17,2467;  18,1104;  Lecre- 
nier,  Chemiker  Zeitung,  13,  1219;  Chittenden,  Pro.  Conn.  Acad. 
Sci.,  Vol.  8. 

Antimony,  when  precipitated  from  a  solution  of  its 
chloride,  or  from  that  of  antimony  potassium  oxalate, 
does  not  adhere  well  to  the  cathode.  It  is  deposited 
very  slowly  from  a  solution  of  potassio-antimony 
tartrate.  Its  deposition  from  a  cold  ammonium  sul- 
phide solution  is  satisfactory,  but  the  use  of  this 
reagent  for  this  purpose  is  not  pleasant,  especially 
when  several  analyses  are  being  carried  out  simulta- 
neously. For  this  reason  potassium  or  sodium  sul- 
phide has  been  substituted.  The  alkaline  sulphide 
used  must  not  contain  iron  or  alumina. 

The  antimony  solution,  mixed  with  sodium  sulphide, 
is  largely  diluted  with  water.  A  more  rapid  reduction 
follows  in  consequence  of  the  dilution.  A  current 
giving  2-3  c.c.  of  electrolytic  gas  per  minute  will  pre- 
cipitate o.i  gram  of  antimony  in  four  or  five  hours. 
To  ascertain  when  all  the  metal  is  deposited  incline 
the  dish  slightly,  thus  exposing  a  clean  platinum  sur- 
face. If  this  remains  bright  for  half  an  hour  the  pre- 
cipitation is  finished.  In  separating  antimony  from 
the  heavy  metals,  e.  g.,  lead,  it  happens  that  alkaline 
sulphides  containing  polysulphides  are  used,  or  are 


55  ELECTRO-CHEMICAL   ANALYSIS. 

produced.  To  remove  these  Classen  proposed  adding 
to  the  antimony-polysulphide  mixture,  already  in  a 
weighed  platinum  dish,  an  ammoniacal  solution  of 
hydrogen  peroxide,  and  warming  the  same  until  the 
liquid  becomes  colorless.  When  this  is  accomplished, 
even  if  a  precipitate  has  been  produced,  add,  after 
cooling,  10  c.c.  of  a  concentrated  solution  of  sodium 
monosulphide,  and  electrolyse  with  a  current  of  1.5-2 
c.c.  electrolytic  gas  per  minute.  Wash  the  deposit 
with  water  and  alcohol. 

Lecrenier  writes  as  follows  relative  to  the  preceding 
method:  The  precipitation  is  all  that  one  can  desire, 
providing  the  solution  of  the  sulpho-salt  is  absolutely 
free  from  polysulphides ;  otherwise,  it  is  incomplete. 
The  antimony  sulphide,  obtained  in  the  ordinary 
course  of  analysis,  always  contains  sulphur,  and  this 
must  be  eliminated.  To  remove  the  various  incon- 
veniences connected  with  the  method  add  50-75  c.c. 
of  a  20  per  cent,  solution  of  sodium  sulphite  to  the 
solution  after  the  addition  of  the  excess  of  sodium 
sulphide,  then  heat  the  liquid  to  complete  decoloriza- 
tion ;  allow  to  cool,  after  which  the  current  is  con- 
ducted through  the  liquid.  This  can  rise  to  5  c.c.  per 
minute  without  impairing  the  result ;  but  it  is  not  best, 
as  the  precipitated  metal  is  then  not  very  coherent. 
It  is  better  to  use  a  current  giving  not  more  than  half 
of  the  above  volume  of  electrolytic  gas  per  minute. 
When  the  quantity  of  antimony  does  not  exceed 
0.2  gram  the  deposit  will  be  adherent  and  free  from 


SEPARATION    OF    METALS.  89 

sulphur ;  wash  with  water,  alcohol  and  ether.  Sulphur 
will  separate  upon  the  anode,  despite  the  presence  of 
an  excess  of  sodium  sulphite.  This,  however,  does 
not  affect  the  result. 

ARSENIC. 

LITERATURE. — Luckow,  Z.  f.  a.  Ch.,  19,  14;  Classen  and  v. 
Reiss,  Ber.,  14,  1622;  Moore,  Ch.  News,  53,  209. 

A  successful  method  for  the  complete  deposition  of 
arsenic  is  not  known.  The  current,  acting  upon  the 
chloride,  causes  complete  volatilization  of  the  metal 
in  the  form  of  arsine.  Its  separation  from  oxalate 
solutions  is  incomplete;  nor  do  the  sulpho-salts 
answer  for  electrolytic  purposes. 


2.   SEPARATION  OF  THE  METALS. 

Electrolysis,  to  be  of  value,  must  not  only  furnish 
the  analyst  with  methods  suitable  for  the  complete 
deposition  of  metals,  but  it  should,  in  addition,  enable 
him  to  separate  metallic  mixtures.  The  data  given 
in  the  preceding  pages  will  serve  for  this  purpose,  but, 
as  special  treatment  is  required  in  some  instances,  a 
brief  outline  of  a  series  of  separations  will  be  indi- 
cated. 


90  ELECTRO-CHEMICAL   ANALYSIS. 

COPPER. 

We  recall,  first  of  all,  that  this  metal  can  be  de- 
posited electrolytically  from  solutions  in  which  free 
nitric  acid  is  present  (p.  51).  This  behavior  renders 
the  separation  of  copper  from  cadmium  possible  (Am. 
Ch.  Jr.,  2,  42).  Place  the  solution  containing  the  two 
metals  in  a  beaker  glass  of  200  c.  c.  capacity  ;  suspend 
(p.  52)  a  weighed  platinum  crucible  in  the  liquid, 
and  precipitate  the  copper  upon  it.  The  total  dilution, 
during  the  decomposition,  should  not  exceed  I5<DC.  c. 
As  much  as  5  per  cent,  of  nitric  acid  can  be  present ; 
the  current  should  give  0.5  c.  c.  electrolytic  gas  per 
minute.  When  all  the  copper  is  precipitated,  washed, 
dried  and  weighed  (p.  51),  make  the  residual  liquid 
alkaline  with  sodium  hydroxide,  and  add  sufficient 
potassium  cyanide  to  redissolve  the  precipitate.  Elec- 
trolyse as  directed  (£.  55).  Copper  and  cadmium 
can  also  be  separated  in  solutions  of  their  double 
alkaline  cyanides  (Jr.  An.  Ch.,^,  385).  Five  to  six 
grams  of  potassium  cyanide  should  be  added  for  every 
0.2-0.4  gram  of  metal.  Do  not  work  with  less  than 
200  c.  c  of  liquid,  and  the  current  should  not  exceed 
0.28  c.c.  of  electrolytic  gas  per  minute.  Under  these 
conditions  the  cadmium  is  deposited,  while  the  copper 
remains  dissolved.  Very  recent  experiments,  made 
in  this  laboratory,  show  that  also  in  the  presence  of  an 
excess  of  free  sulphuric  acid  the  current  will  precipi- 
tate copper  free  from  cadmium:  e.g.,  0.1975  gram  of 


SEPARATION    OF    METALS COPPER.  9 1 

metallic  copper,  and  0.1828  gram  of  cadmium,  both  as 
sulphates,  were  dissolved  in  20  c.  c.  of  water ;  to  this 
were  added  10  c.  c.  of  sulphuric  acid,  of  1.09  sp.  gr. 
and  100  c.  c.  of  water.  The  current  gave  0.30  c.  c. 
electrolytic  gas  per  minute.  The  precipitated  copper 
weighed  0.1976  gram;  it  contained  no  cadmium. 

It  is  not  possible  to  separate  these  metals  when 
present  together  in  an  oxalate  solution. 

The  precipitation  of  copper  in  nitric  acid  solutions 
further  enables  us  to  separate  it  from  iron,  aluminium, 
chromium,  cobalt,  nickel,  zinc,  the  alkaline  earth  and 
the  alkaline  metals,  though  it  would  perhaps  be  better 
to  execute  the  separation  from  the  first  six  in  a  solu- 
tion containing  free  sulphuric  acid.  From  mercury, 
silver  and  bismuth  the  copper  cannot  be  separated  in 
the  presence  of  nitric  or  sulphuric  acid.  For  the  elec- 
trolytic separation  of  copper  from  mercury  see  p.  97. 
Its  separation  from  bismuth  has  only  recently  been 
made  possible  by  combining  the  behavior  of  copper 
in  the  presence  of  an  excess  of  alkaline  cyanide,  and 
that  of  bismuth  where  it  exists  as  a  double  citrate  in 
an  alkaline  solution  (p.  60).  Add  3-4  grams  of  citric 
acid  to  the  bismuth  solution,  so  that  upon  the  later 
addition  of  sodium  hydroxide  to  alkaline  reaction  a 
precipitate  is  not  produced.  Into  this  liquid  introduce 
the  cyanide  copper  solution,  and  electrolyse  with  a 
current  giving  0.15  c.c.  electrolytic  gas  per  minute. 

In  a  solution  of  copper  and  lead,  containing  5  per  cent, 
of  nitric  acid,  the  former  will  be  deposited  completely 


92  ELECTRO-CHEMICAL   ANALYSIS. 

at  the  cathode,  while  the  latter  is  fully  precipitated  as  di- 
oxide at  the  anode  (p.  62).  This  course  is  adopted  when 
separating  these  metals  in  alloys  or  minerals  (p.  63). 

The  separation  of  copper  from  manganese  should 
be  conducted  in  solutions  containing  a  slight  excess 
of  sulphuric  acid.  While  the  copper  is  deposited  as 
such  upon  the  cathode,  the  manganese  separates  upon 
the  anode  as  dioxide  (p.  76).  A  platinum  foil  may  be 
used  as  anode  in  this  separation.  Another  method, 
applicable  here,  is  based  on  the  observation  that  man- 
ganese remains  dissolved  in  the  presence  of  phos- 
phoric acid,  while  the  copper  is  deposited  in  its  usual 
form.  For  example,  0.1770  gram  copper  and  0.1500 
gram  manganese,  both  as  sulphates,  were  treated  with 
30  c.cr  of  sodium  phosphate,  of  sp.  gr.  1.0388,  and  10 
c.c.  phosphoric  acid,  of  sp.  gr.  1.347,  trien  diluted  to 
1 50  c.c.  with  water  and  electrolysed  with  a  current 
giving  I  c.c.  of  electrolytic  gas  per  minute.  The  pre- 
cipitated copper  weighed  0.1765  gram.  Manganese 
did  not  separate,  even  as  dioxide.  (See  Am.  Ch.  Jr., 

12,   329.) 

The  deposition  of  copper  in  the  presence  of  anti- 
mony is  yet  unsatisfactory.  When  the  latter  does  not 
exceed  j£  of  the  quantity  of  the  first,  no  fault  can  be 
found  with  the  separation  (p.  39,  and  Wrightson,  Z.  f. 
a.  Ch.,  15,  297). 

As  to  the  separation  of  copper  from  arsenic,  Classen 
remarks  (Ber.,  15,  297),  that  when  the  arsenic  exceeds 
0.20  per  cent.,  the  deposited  copper  is  more  or  less 


SEPARATION    OF   METALS COPPER.  93 

dark  in  color,  and  the  result  will  be  high.  Some 
chemists  have  advised  that  after  the  copper  deposit 
has  been  dried,  it  should  be  heated  to  volatilize  the 
arsenic ;  the  residual  cupric  oxide  is  redissolved  and 
its  solution  again  electrolysed.  This  procedure  will 
be  satisfactory  when  arsenic  is  present  in  traces,  other- 
wise it  is  worthless.  The  arsenic  in  copper  ores  can 
be  entirely  removed  by  evaporating  their  acid  solution 
with  bromine,  when  it  will  be  expelled  as  bromide. 
The  copper  results  are  then  satisfactory. 

McCay  (Chemiker  Zeitung,  14,  509)  has  observed 
that  when  the  current  from  4-6  Meidjnger  cells  is  con- 
ducted through  a  potassium  arsenite  solution,  made 
distinctly  alkaline  with  ammonium  hydroxide,  this 
salt  sustains  no  change.  With  copper,  under  like  con- 
ditions, the  separation  of  the  metal  is  quantitative. 
Upon  this  behavior  he  bases  a  very  excellent  separa- 
tion of  these  two  metals.  The  only  care  necessary  is 
to  see  that  not  too  much  ammonia  is  employed.  In 
this  laboratory  like  results  were  obtained,  but  prefer- 
ence has  since  been  given  to  the  following  course : 
Add  the  copper  solution  to  that  of  the  alkaline  arsen- 
ite or  arsenate,  and  follow  it  with  a  solution  of  potas- 
sium cyanide  until  the  precipitate  first  produced  is 
just  dissolved;  the  liquid  will  then  show  a  slight 
purple  tint.  A  current  of  0.25  c.c.  electrolytic  gas 
per  minute,  precipitates  the  copper  quite  rapidly 
under  these  conditions ;  the  deposit  will  contain  no 
arsenic  (Am.  Ch.  Jr.,  12,  428). 


94  ELECTRO-CHEMICAL  ANALYSIS. 

When  antimony,  arsenic  and  tin  are  associated  with 
copper,  treat  the  sulphides  with  sodium  sulphide. 
The  resulting  alkaline  sulphide  solution  can  then  be 
employed  for  the  separation  of  the  first  three  (p.  102), 
while  the  insoluble  copper  sulphide  may  be  dissolved 
and  treated  as  described  on  page  54. 


CADMIUM. 

The  methods  already  described  under  copper  are 
sufficient  for  the  separation  of  cadmium  from  this 
metal.  A  solution  containing  free  nitric  acid  is  used 
for  the  separation  of  cadmium  from  silver,  mercury, 
lead  and  bismuth ;  the  latter  is  also  separated  from  it 
by  using  a  solution  in  which  there  is  a  slight  excess 
of  sulphuric  acid  (p.  60).  When  these  metals  have 
been  removed  from  their  solution,  neutralize  the 
excess  of  acid  with  potassium  hydroxide,  add  a  slight 
excess  of  potassium  cyanide  and  electrolyse  the  liquid 
for  the  estimation  of  the  cadmium,  as  directed  on 
page  55- 

When  there  is  an  excess  of  but  2  c.c.  of  sulphuric 
acid,  of  sp.  gr.  1.09,  cadmium  can  be  precipitated 
(p.  55),  and  thus  separated  from  iron,  aluminium,  chro- 
mium, zinc,  cobalt,  nickel  and  manganese  (the  latter 
deposits  at  the  same  time  as  dioxide  upon  the  anode, 
p.  76).  Another  method  which  serves  for  the  separa- 
tion of  cadmium  from  either  zinc  or  cobalt,  consists 
in  having  these  metals  in  solution  in  the  form  of 


SEPARATION    OF    METALS CADMIUM.  95 

double  cyanides  with  the  alkaline  cyanides.  The 
volume  of  the  aqueous  solution  should  be  at  least 
200  c.c. ;  to  this  add  4^  grams  of  potassium  cyanide, 
and  electrolyse  the  liquid  with  a  current  giving  0.30 
c.c.  electrolytic  gas  per  minute  (Am.  Ch.  Jr.,  n,  p. 
352).  Cadmium  cannot  be  separated  from  nickel  by 
this  method. 

Under  the  special  methods  given  for  the  estimation 
of  cadmium  (p.  55)  it  was  mentioned  that  it  separates 
well  from  solutions  of  the  acetate.  Yver  (B.  s.  Ch. 
Paris,  34,  18)  has  employed  this  behavior  to  separate 
cadmium  from  zinc.  The  method  is  this  :  the  metals 
are  converted  into  acetates  by  the  addition  of  2-3 
grams  of  sodium  acetate  to  their  solution,  followed 
by  several  drops  of  free  acetic  acid.  This  liquid  is 
then  exposed  to  the  current  from  two  ordinary  Daniell 
cells.  Heat  (70°)  the  solution  during  the  decomposi- 
tion. The  precipitated  cadmium  contains  no  zinc. 
Three  to  four  hours  are  necessary  for  the  reduction 
of  0.18-0.210  gram  of  cadmium.  Remove  the  zinc 
from  the  filtrate  by  the  method  of  Riche  (p.  71). 
Smith  and  Knerr  (Am.  Ch.  Jr.,  8,  210)  have  tried  this 
separation,  and  recommend  that  the  current  should 
not  exceed  0.1—0.2  c.c.  of  electrolytic  gas  per  minute. 
It  is  also  essential  that  the  liquid  be  held  at  a  nearly 
uniform  temperature  (70°)  during  the  reduction.  The 
dilution  of  the  liquid  should  not  exceed  100  c.c. 

The  same  chemists  also  (Am.  Ch.  Jr.,  8,  210) 
found  that  upon  electrolysing  a  solution  of  these  two 


96  ELECTRO-CHEMICAL   ANALYSIS. 

metals,  to  which  3-4  grams  of  sodium  tartrate  and 
tartaric  acid  had  been  added,  with  a  current  of  3-4 
c.c.  electrolytic  gas  per  minute,  tKe  cadmium  was 
deposited  completely  from  the  warm  solution,  and 
contained  no  zinc. 

Eliasberg  (Z.  f.  a.  Ch.,  24,  550)  has  also  proposed 
a  method  for  the  separation  of  cadmium  from  zinc : 
Dissolve  the  metallic  oxides  in  hydrochloric  acid, 
evaporate  their  solution  to  dryness,  add  8-10  grams 
of  potassium  oxalate,  and  2-3  grams  of  ammonium 
oxalate,  diluting  finally  to  100  c.c. ;  heat  "to  boiling 
and  electrolyse  the  warm  (not  boiling)  liquid  with  a 
current  equal  to  0.15  c.c.  electrolytic  gas  per  minute. 
Cover  the  vessel  in  which  the  decomposition  is  made. 
Six  to  seven  hours'  will  be  required  for  the  com- 
plete deposition  of  0.15  gram  of  metal  (cadmium). 
The  electrolytic  separation  of  these  two  metals  is  also 
possible  in  a  solution  of  their  phosphates,  dissolved 
in  phosphoric  acid  (Am.  Ch.  Jr.,  12,  329). 

To  separate  cadmium  from  antimony  and  tin  it  is 
necessary  to  have  recourse  to  the  usual  method  of 
analysis,  the  solubility  of  the  sulphides  of  the  first 
two  in  alkaline  sulphides.  A  direct  separation  of 
cadmium  from  arsenic  is  possible,  but  that  the  cad- 
mium may  be  precipitated  absolutely  free  from 
arsenic,  the  latter  must  be  present  in  the  solution  as 
an  arsenate.  Upon  adding  two  grams  of  potassium 
cyanide  to  such  a  solution,  and  electrolysing  the  same 
with  a  current  equal  to  0.3  c.c.  of  electrolytic  gas  per 


SEPARATION    OF    METALS MERCURY.  97 

minute,  the  cadmium  will  be  completely  precipitated 
in  ten  hours.  The  reduction  is  made  in  cold  solu- 
tions (Am.  Ch.  Jr.,  12,  p.  428). 


MERCURY. 

This  metal  is  deposited  quite  rapidly  from  solutions 
containing  free  nitric  acid  (p.  57),  hence  under  such 
conditions  it  may  be  separated  from  cadmium,  iron, 
aluminium,  chromium,  zinc,  nickel,  cobalt,  barium, 
strontium,  calcium,  magnesium  and  the  alkalies.  When 
lead  and  mercury  are  exposed,  in  a  solution  of  nitric 
acid,  to  the  action  of  the  current,  they  are  deposited 
simultaneously,  the  lead  as  dioxide  at  the  anode 
(p.  62),  and  the  mercury  as  metal  upon  the  cathode. 
Manganese  and  mercury  are  separated  to  the  best 
advantage  in  solutions  containing  free  sulphuric  acid 
(p.  76).  Mercury  cannot  be  separated  in  the  electro- 
lytic way  from  silver  and  bismuth.  From  copper,  as 
long  as  the  quantity  of  this  metal  does  not  exceed  20 
per  cent,  of  that  of  the  mercury,  the  separation  can  be 
made  in  a  cyanide  solution  (Jr.  An.  Ch.,  3,  254).  As 
an  example,  it  may  be  stated  that  0.1833  gram  mer- 
cury, as  chloride,  and  0.0259  gram  copper,  as  sul- 
phate, with  1.5  grams  potassium  cyanide,  were  diluted 
to  200  c.c.  with  water,  and  then  electrolysed  in  the 
cold,  with  a  current  giving  0.32  c.c.  of  electrolytic  gas 
per  minute.  At  the  end  of  sixteen  hours  0.1833  gram 
mercury  had  separated. 


98  ELECTRO-CHEMICAL    ANALYSIS. 

More  recent  experiments,  made  in  this  laboratory, 
prove  that  mercury  may  be  readily  separated  in  the 
same  way  from  zinc,  nickel  and  cobalt.  The  quantity 
of  alkaline  cyanide  to  be  used  in  these  separations 
may  vary  from  three  to  four  grams,  although  when 
cobalt  is  to  be  separated  from  mercury  good  results 
will  not  be  obtained  if  more  than  three  grams  of  potas- 
sium cyanide  are  present  for  0.3—0.4  gram  of  metal. 
The  current  should  not  exceed  0.8  c.c.  of  electrolytic 
gas  per  minute  (Am.  Ch.  Jr.,  12,  104). 

In  separating  mercury  from  tin  and  antimony,  pre- 
pare their  sulphides,  and  digest  these  with  ammonium 
sulphide,  dissolving  out  the  first  two.  The  residual 
mercury  sulphide  is  then  dissolved  in  aqua  regia,  and 
after  neutralizing  the  excess  of  acid  with  an  alkaline 
hydroxide,  potassium  cyanide  is  added  in  sufficient 
quantity  to  form  the  double  cyanide,  which  is  then 
electrolysed  as  described,  p.  58.  Mercury  is  separated 
from  arsenic  similarly  to  cadmium  from  this  metal, 
although  it  is  immaterial  whether  the  arsenic  exists 
in  the  solution  as  an  arsenite  or  arsenate  (p.  96). 


BISMUTH. 

At  present  there  is  no  satisfactory  electrolytic 
method  known  for  the  separation  of  this  metal  from 
mercury,  silver  and  lead.  Its  separation  from  cad- 
mium is  effected  in  solutions  containing  free  sulphuric 
acid  (5-10  c.c.  of  sp.  gr.  1.09),  p.  60.  This  course  will 


SEPARATION    OF    METALS LEAD.  99 

also  serve  to  separate  it  from  iron,  manganese,  zinc, 
nickel,  cobalt,  aluminium,  chromium,  uranium,  mag- 
nesium and  the  alkaline  metals  (p.  60).  The  method 
of  Eliasberg  (p.  59)  may  also  be  used  for  the  separa- 
tion of  bismuth  from  zinc,  nickel,  cobalt  and  uranium. 
In  separating  bismuth  from  those  metals  the  sulphides 
of  which  are  soluble  in  alkaline  sulphides,  it  is  neces- 
sary to  have  the  usual  gravimetric  course  precede  the 
electrolytic  reduction. 

LEAD. 

The  deposition  of  lead  as  dioxide  upon  the  anode 
(p.  62)  in  the  presence  of  at  least  five  per  cent,  of 
nitric  acid  affords  a  method  for  its  separation  from 
mercury,  silver,  copper,  cadmium,  iron,  chromium, 
aluminium,  zinc,  nickel,  cobalt,  uranium,  the  metals 
of  the  alkaline  earths  and  the  alkaline  metals.  It 
will  be  remembered,  of  course,  that  some  of  these 
metals  separate  as  such  upon  the  cathode  simultane- 
ously with  the  lead  upon  the  anode.  Lead,  in  some 
respects,  is  much  like  manganese,  from  which  it  can- 
not be  separated  electrolytically.  Its  deposition  re- 
quires no  special  description,  as  the  conditions  already 
described  upon  p.  63  are  to  be  observed  in  the  per- 
formance of  the  separations  just  indicated.  Lead,  tin, 
antimony  and  arsenic  are  separated  as  directed  under 
the  preceding  heavy  metals.  Follow  the  ordinary 
gravimetric  course. 

Lead  dioxide,  like  manganese  dioxide  (p.  76),  is 


IOO  ELECTRO-CHEMICAL   ANALYSIS. 

not  separated  from  solutions  containing  an  excess  of 
an  alkaline  sulphocyanide,  and,  if  already  precipitated 
as  dioxide,  will  redissolve  upon  the  addition  of  the 
sulphocyanide. 

SILVER. 

To  separate  silver  and  copper  electrolytically,  mix 
equal  quantities  of  the  two  metals,  in  the  form  of 
nitrates,  with  four  and  one-half  grams  of  potassium 
cyanide,  dilute  to  200  c.c.  with  water,  and  electrolyse 
with  a  current,  giving  0.15-0.80  c.c.  electrolytic  gas 
per  minute  (Am.  Ch.  Jr.,  12,  104).  As  much  as  0.2 
gram  of  silver  will  be  deposited  in  12—14  hours.  If 
desirable,  expose  the  filtrate  containing  the  copper  to 
the  action  of  a  stronger  current  (3  c.c.  O-H  gas  per 
minute) ;  as  soon  as  the  excess  of  alkaline  cyanide  is 
decomposed,  the  copper  will  be  deposited  in  a  dense 
and  brilliant  coating.  Proceed  as  directed  (p.  94)  in 
separating  silver  from  cadmium.  There  is  no  known 
electrolytic  method  for  the  separation  of  silver  from 
mercury.  It  is  true  both  can  be  precipitated  from  a 
nitric  acid  solution  (pp.  57,  64),  their  joint  weight 
determined,  after  which  the  mercury  can  be  expelled 
by  heat  and  the  silver  residue  be  re-weighed. 

There  is  no  electrolytic  method  known  for  the 
separation  of  silver  from  bismuth.  The  separation  of 
silver  from  lead  is  made  in  a  nitric  acid  solution  (p. 
64).  A  similar  solution  is  used  to  separate  it  from 
the  metals  of  other  groups. 


SEPARATION   OF   METALS SILVER.  IOI 

When  antimony,  tin  and  silver  are  present  together, 
digest  their  sulphides  with  sodium  sulphide,  which 
will  bring  the  antimony  and  tin  into  a  proper  condition 
to  effect  their  separation  electrolytically  (p.  102).  The 
insoluble  silver  sulphide  is  dissolved  in  nitric  acid, 
and,  after  the  excess  of  the  latter  is  expelled,  potas- 
sium cyanide  is  added  in  excess  and  the  resulting 
liquid  electrolysed  in  the  cold,  with  a  feeble  current. 
The  silver  is  deposited  as  a  dense  coating,  and  may 
be  washed  with  hot  water. 

It  is  possible  to  separate  silver  from  arsenic  in  the 
presence  of  three  grams  of  potassium  cyanide,  pro- 
viding the  arsenic  exists  in  the  solution  as  an  arsenate. 
A  current,  giving  0.30  c.c.  electrolytic  gas  per  minute, 
will  be  sufficient  for  the  metallic  reduction.  Deter- 
mine the  arsenic  in  the  residual  liquid  by  the  usual 
gravimetric  method  (Am.  Ch.  Jr.,  12,  p.  428). 

The  course  just  described  (above)  for  the  separation 
of  silver  from  copper  will  answer  admirably  for  the 
same  purpose  with  silver,  zinc,  nickel  and  cobalt.  Not 
more  than  three  grams  of  potassium  cyanide  are  re- 
quired for  0.2  gram  of  each  metal.  The  total  dilution 
should  not  be  less  than  200  c.c.,  and  the  current  not 
stronger  than  0.3  c.c.  electrolytic  gas  per  minute. 


102  ELECTRO-CHEMICAL   ANALYSIS. 

Much  credit  is  due  Classen  and  his  co-laborers  for 
valuable  data  upon  the  electrolytic  separation  of  the 
following  metals : — 


ANTIMONY    FROM    TIN. 

The  sulphides  (or  residue  from  a  solution  of  the 
metals)  are  placed  in  a  weighed  platinum  dish,  and 
covered  with  60  c.c.  of  sodium  monosulphide,  to  which 
is  added  one  gram  of  sodium  hydroxide.  If  imme- 
diate solution  does  not  occur,  apply  heat,  then  cool. 
Conduct  a  current  of  1.5-2.0  c.c.  of  electrolytic  gas 
per  minute  through  this  mixture.  When  the  reduc- 
tion is  finished,  pour  off  the  liquid  into  a  second  dish. 
Treat  the  antimony  deposit  as  already  directed  (p. 
87).  To  prepare  the  tin  solution  for  electrolysis,  pro- 
ceed as  described  (p.  86)  for  the  conversion  of  the 
sodium  into  ammonium  sulphide  (Ber.,  17,  2245  ;  18, 
1 1 10). 

ANTIMONY  FROM  ARSENIC. 

These  metals,  or  compounds  of  the  same,  are  evapor- 
ated to  dryness  with  aqua  regia,  the  residue  dissolved 
in  2—3  c.c.  of  water ;  concentrated  sodium  hydroxide  is 
added  so  that  there  will  be  one  gram  of  alkali  present 
in  the  liquid,  and  finally  add  60  c.c.  of  sodium  mono- 
sulphide.  Electrolyse  as  in  the  separation  of  anti- 
mony from  tin  (Ber.,  19,  323). 

If  antimony,  arsenic  and  tin  are  present  together, 


SEPARATION    OF    IRON    FROM    MANGANESE.          103 

the  arsenic  is  expelled  from  their  solution  by  the 
Fischer-Hufschmidt  method  (Ber.,  18,  1 1 10),  and  the 
separation  of  the  tin  and  antimony  made  as  already 
directed  on  the  preceding  page. 

In  general  analysis  phosphoric  acid  is  frequently 
precipitated  as  tin  phosphate.  The  latter,  of  course, 
contains  oxide  of  tin.  Dissolve  the  precipitate  in 
ammonium  sulphide.  On  electrolysing  the  solution 
the  tin  is  precipitated,  and  the  filtrate  will  contain  all 
the  phosphoric  acid;  this  can  be  estimated  in  the 
usual  way  (Classen).  By  observing  this  suggestion 
the  determination  of  the  phosphoric  acid  in  a  separate 
portion  of  the  material  will  not  be  required. 


IRON,  MANGANESE,  ZINC,    NICKEL,  COBALT,  ALU- 
MINIUM, CHROMIUM  AND  PHOSPHORIC  ACID. 

Electrolytic  methods  for  the  separation  of  these 
metals  are  not  either  so  numerous,  nor  so  thoroughly 
worked  out  as  with  the  metals  already  considered. 
Their  separation  from  the  heavy  metals  has  been  out- 
lined under  these,  and  it  only  remains  to  describe  the 
courses  which  may  be  pursued  with  this  group  of 
metals  when  present  together. 

Concerning  the  separation  of  iron  from  manganese, 
it  should  be  remembered  that  objections  have  been 
offered  to  the  suggestion  of  Classen  (Ber.,  18,  1787), 
hence  to  obtain  results  at  all  satisfactory  it  is  advisable 
to  carry  out  the  separation  exactly  as  given  by  this 


IO4  ELECTRO-CHEMICAL   ANALYSIS. 

chemist :  "  If  a  solution  of  the  double  oxalates  of  iron 
and  manganese  is  subjected  to  electrolysis,  without 
the  previous  addition  of  a  great  excess  of  ammonium 
oxalate  .....  it  is  impossible  to  obtain  a 
quantitative  separation  of  the  two  metals,  because  the 
manganese  dioxide  carries  down  with  it  considerable 
quantities  of  ferric  hydroxide.  The  complete  sepa- 
ration of  the  metals  is  possible  only  when  the  sepa- 
ration of  the  dioxide  is  delayed  till  most  of  the  iron 
is  precipitated."  The  electrolysis  in  the  cold  is  not 
favorable ;  the  large  amount  of  ammonium  carbonate, 
or  ammonia  formed  in  the  decomposition  of  the  ex- 
cessive ammonium  oxalate  dissolves  the  precipitated 
dioxide.  "  The  rapid  dissociation  of  ammonium  oxa- 
late when  heated,  however,  gives  a  simple  means  of 
delaying,  or  entirely  preventing,  the  formation  of  a 
manganese  precipitate  during  the  electrolysis."  The 
solution  containing  the  two  metals  is  treated  with  5—6 
grams  of  ammonium  oxalate,  and  while  hot  is  acted 
upon  with  a  current  giving  1 5-20  c.c.  of  electrolytic 
gas  per  minute.  Treat  the  iron  deposit  as  directed 
on  p.  78.  Boil  the  liquid,  poured  off  from  the  iron, 
with  sodium  hydroxide,  to  decompose  the  ammonium 
carbonate  present,  after  which  add  sodium  carbonate 
and  a  little  sodium  hypochlorite.  The  manganese 
is  precipitated  as  dioxide,  and  finally  weighed  as  the 
protosesquioxide.  Nickel  and  manganese  are  sepa- 
rated from  each  other  in  a  similar  manner.  Cobalt 
and  zinc,  when  present  with  manganese,  are  separated 


SEPARATION    OF    IRON    FROM    ZINC.  IO5 

from  it  by  a  current  of  10  c.c.  oxy-hydrogen  gas  per 
minute,  acting  in  the  cold.  Oxalic  acid  is  added 
toward  the  end  of  the  reduction  to  redissolve  any 
separated  manganese  dioxide. 

To  separate  iron  from  zinc,  add  1-3  c.c.  of  a  solu- 
tion of  potassium  oxalate  (i  :  3)  and  3-4  grams  of 
ammonium  oxalate  to  their  solution,  and  electrolyse 
the  liquid  with  a  current  liberating  10-12  c.c.  electro- 
lytic gas  per  minute.  The  zinc  is  deposited  first,  and 
no  difficulty  is  experienced,  providing  its  quantity  is 
less  than  one-third  that  of  the  iron  present.  Classen 
provides  for  this  condition  by  adding  a  weighed 
amount  of  pure  ferrous  ammonium  sulphate  in  excess. 
The  same  chemist  precipitates  iron  and  cobalt  simul- 
taneously from  their  double  oxalate  solution  (condi- 
tions as  above),  takes  the  combined  weight  of  the 
metals,  dissolves  them  in  acid  and  determines  the  iron 
by  titration  ;  the  cobalt  is  found  by  difference.  Nickel 
and  iron  are  also  deposited  together  (same  as  cobalt 
and  iron)  as  an  alloy,  which  is  weighed,  then  dissolved 
in  concentrated  hydrochloric  acid,  the  iron  oxidized, 
and  the  ferric  solution  titrated  with  a  stannous  chloride 
solution.  It  will  be  observed  that  an  electrolytic 
separation  of  zinc  from  cobalt  and  nickel,  and 'the 
latter  from  each  other  is  wanting. 

The  writer  would  recommend  the  following  course 

in  separating  the  metals  of  this  group :  Separate  the 

iron  from  the  manganese,  zinc,  nickel  and  cobalt,  by 

precipitation   with   barium    carbonate.     Dissolve   the 

H 


IO6  ELECTRO-CHEMICAL    ANALYSIS. 

iron  precipitate  in  citric  acid,  and  electrolyse  the 
solution  according  to  the  directions  given  upon  page 
79.  The  filtrate,  containing  the  zinc,  manganese, 
nickel  and  cobalt,  together  with  a  little  barium  salt, 
is  carefully  treated  with  just  sufficient  dilute  sulphuric 
acid  to  remove  the  barium.  After  filtering,  electrolyse 
the  filtrate  in  a  platinum  dish,  connected  with  the 
anode  of  a  battery,  yielding  3—5  c.c.  of  electrolytic 
gas  per  minute.  A  weighed  piece  of  platinum  foil 
will  answer  for  the  cathode.  The  manganese  is  de- 
posited as  dioxide  (p.  76) ;  the  other  metals  remain  dis- 
solved and  can  only  be  separated  by  one  of  the  usual 
gravimetric  methods.  This  course  proved  quite  satis- 
factory in  the  analysis  of  the  mineral  franklinite,  where, 
after  having  obtained  the  iron  and  manganese  as 
described,  the  zinc  was  also  determined  electrolytically 
in  the  liquid  poured  off  from  the  manganese  deposit. 
If  the  solution  containing  these  two  metals  be  very 
slightly  acid  with  sulphuric  acid,  they  can  be  precipi- 
tated simultaneously — the  zinc  at  the  cathode,  and 
manganese  dioxide  at  the  anode. 

Iron  can  be  further  separated,  in  citrate  solution, 
from  aluminium,  chromium  and  titanium  (p.  79). 
The  deposition  should  occur  in  a  cold  solution,  with 
a  current,  liberating  12  c.c.  electrolytic  gas  per  minute. 
This  method  will  also  serve  to  separate  iron  from 
chromium  and  phosphoric  acid.  Classen  separates 
iron,  cobalt,  nickel  and  zinc  from  manganese,  chromium 
and  aluminium  by  electrolysing  their  hot  oxalate  solu- 


SEPARATION    OF    MERCURY    AND    PALLADIUM.        IO/ 

tion  in  the  presence  of  a  large  excess  of  ammonium 
oxalate.  The  first  four  are  deposited  as  metals,  while 
the  manganese  dioxide  upon  the  anode  has  carried 
with  it  some  chromium,  and  should  be  dissolved,  and 
the  manganese  reprecipitated  by  sodium  hydroxide 
and  sodium  hypochlorite  (p.  104).  The  main  solu- 
tion from  the  metals  is  digested  until  the  excess  of 
ammonia  is  expelled,  when  the  aluminium  hydroxide 
is  filtered  off;  the  chromate  solution,  then  reduced 
with  hydrogen  sulphide  in  the  presence  of  an  acid,  is 
precipitated  with  ammonium,  hydroxide.  In  all  cases 
where  it  is  necessary  to  add  oxalic  acid  to  redissolve 
the  aluminium  hydroxide,  or  manganese  dioxide,  the 
acid  should  be  introduced  without  the  interruption  of 
the  current.  When  phosphoric  acid  is  present  with 
the  iron  and  manganese  it  will  be  found  in  the  liquid 
(oxalate)  from  which  the  metals  have  been  previously 
precipitated,  and  may  be  removed  as  ammonium 
magnesium  phosphate. 

Little  can  be  said  relative  to  the  separation  of  the 
rarer  metals ;  further  investigation  is  required  in  this 
direction. 

Quite  recent  experiments,  made  in  this  laboratory, 
show  that  mercury  and  palladium  can  be  separated  if 
present  together  in  a  solution  containing  not  less  than 
3  grams  of  potassium  cyanide  for  0.2-0.4  gram  of  the 
metals.  The  current  necessary  here  may  vary  from 


IO8  ELECTRO-CHEMICAL   ANALYSIS. 

0.08  c.c.— 0.22  c.c.  electrolytic  gas  per  minute.  Not- 
withstanding that  cadmium  and  silver  are  easily 
precipitated  from  their  double  cyanide  solutions,  it  is 
impossible  to  separate  them  from  palladium.  In  fact, 
they  appear  to  hasten  the  deposition  of  the  latter 
metal. 

Mercury,  silver  and  cadmium,  furthermore,  can  be 
separated  from  solutions  containing  excess  of  alkaline 
cyanide  together  with  tungstic  and  molybdic  acids, 
without  carrying  down  any  of  the  latter.  The  con- 
ditions most  favorable  for  these  separations  are 
perfectly  similar  to  those  just  given  above  (pp.  96,  98, 
101)  for  the  separation  of  these  metals  from  arsenic 
(Am.  Ch.  Jr.,  12,  p.  428). 


3.  OXIDATIONS    BY   MEANS   OF   THE 
ELECTRIC  CURRENT. 

When  natural  sulphides,  e.g.,  chalcopyrite,  marca- 
site,  etc.,  are  exposed  to  the  action  of  a  strong  current 
in  the  presence  of  a  sufficient  quantity  of  potassium 
hydroxide  their  sulphur  will  be  quickly  and  fully 
oxidized  to  sulphuric  acid  (Jr.  Fr.  Ins.,  April,  1889, 
Ber.,  22,  1019).  The  metals  (iron,  copper,  etc.)  orig- 
inally present  in  the  mineral  separate  as  oxides  and 
metal  on  dissolving  the  fused  alkaline  mass  in  water. 
This  method  of  oxidation  eliminates  many  other 
disagreeable  features  of  the  old  methods.  Its  rapidity 


OXIDATIONS    BY    MEANS    OF    CURRENT.  1 09 

and  accuracy  entitle  it  to  the  following  brief  descrip- 
tion : — 

Place  about  20  grams  of  caustic  potash  in  a  nickel 
crucible  i^  inches  high  and  i%&  inches  wide.  Apply 
heat  from  a  Bunsen  burner  until  the  water  has  been 
almost  entirely  expelled,  when  the  flame  is  lowered  so 
that  the  temperature  is  just  sufficient  to  retain  the 
alkali  in  a  liquid  condition.  The  crucible  is  next 
connected  with  the  negative  pole  of  a  battery,  and  the 
sulphide  to  be  oxidized  is  placed  upon  the  fused 
alkali.  As  some  natural  sulphides  part  with  a  portion 
of  their  sulphur  at  a  comparatively  low  temperature, 
it  is  advisable  to  allow  the  alkali  to  cool  so  far  that  a 
scum  forms  over  its  surface,  before  adding  the 
weighed  mineral. 

The  heavy  platinum  wire,  attached  to  the  anode, 
extends  a  short  distance  below  the  surface  of  the 
fused  mass.  When  the  current  passes  a  lively  action 
ensues,  accompanied  with  some  spattering.  To  pre- 
vent loss  from  this  source,  always  place  a  perforated 
watch-crystal  over  the  crucible.  After  the  current 
has  acted  for  10-20  minutes  interrupt  it.  When  the 
crucible  and  its  contents  are  cold  place  them  in  about 
200  c.c.  of  water,  to  dissolve  out  the  excess  of  alkali 
and  alkaline  sulphate.  Filter.  Invariably  examine 
the  residue  for  sulphur,  by  dissolving  it  in  nitric  acid 
and  then  testing  with  barium  chloride.  The  alkaline 
filtrate  is  carefully  acidulated  with  hydrochloric  acid, 
and  after  digesting  for  some  time,  is  precipitated  with 


1 10  ELECTRO-CHEMICAL   ANALYSIS. 

a  boiling  solution  of  barium  chloride.  When  the 
hydrochloric  acid  is  first  added,  care  should  be  taken 
to  observe  whether  hydrogen  sulphide  or  sulphur 
dioxide  is  liberated.  If  the  oxidation  is  incomplete 
sulphur  also  makes  its  appearance  as  a  white  tur- 
bidity. The  caustic  potash  employed  in  these  oxida- 
tions should  always  be  examined  for  sulphur  and 
other  impurities.  As  it  is  difficult  to  obtain  alkali 
perfectly  free  from  sulphur  compounds,  a  weighed 
portion  should  be  taken  and  its  quantity  of  sulphur 
deducted  from  that  actually  found  in  the  analysis. 

The  arrangement  of  apparatus  employed  in  the 
oxidations  just  outlined  is  represented  in  Fig.  25. 
The  crucible  A  is  supported  by  a  stout  copper  wire 
bent  as  indicated,  and  held  in  position  by  a  binding 
screw  attached  to  the  base  of  a  filter  stand.  The  arm 
of  the  latter  carries  a  second  binding  screw  holding 
the  platinum  anode  in  position.  While  the  platinum 
rod  is  generally  the  positive  electrode,  it  is  best  to 
make  it  the  negative  pole  for  at  least  a  part  of  the 
time  during  which  the  current  acts.  This  is  advisable 
because  in  many  of  the  decompositions  metals  are 
precipitated  upon  the  sides  of  the  crucibles,  and  can 
readily  enclose  unattacked  sulphide,  so  that  by  revers- 
ing the  current  (the  poles)  any  precipitated  metal  will 
be  detached,  and  the  enclosed  sulphide  be  again 
brought  into  the  field  of  oxidation.  Cinnabar  is  a 
sulphide  which  has  a  tendency  to  mass  together,  and 
it  could  only  be  decomposed  and  its  sulphur  thor- 


OXIDATIONS    BY    MEANS    OF    CURRENT. 


112  ELECTRO-CHEMICAL   ANALYSIS. 

oughly  oxidized  by  reversing  the  current  every  few 
minutes.  To  reverse  the  current  use  the  contrivance 
C\  this  is  nothing  more  than  a  square  block  of  wood 
fastened  to  the  top  of  the  table  T,  by  a  screw  or  nail. 
The  four  depressions  (x)  in  it  contain  a  few  drops  of 
mercury,  into  which  the  side  binding  screws  (a)  pro- 
ject. The  mercury  cups  are  made  to  communicate 
with  each  other  by  a  cap  of  wood,  D,  carrying  two 
metallic  wires,  which  pass  through  it  and  project  a 
slight  distance  on  its  lower  side.  By  raising  the  cap 
and  turning  it  so  that  the  wires  are  vertical  (J)  or 
horizontal  (*->),  the  crucible  or  the  platinum  wire 
extending  into  the  fused  mass  can  be  made  the  anode 
or  cathode  in  a  few  seconds.  E  is  a  Kohlrausch 
amperemeter  (Fig.  15),  and  R  the  resistance  frame 

(Fig-  13)- 

Storage  batteries  furnish  the  most  satisfactory  cur- 
rent for  work  of  this  character.  In  the  sketch  the 
cells  stand  beneath  the  table  ;  the  wire  from  the  anode 
passes  through  a  hole  in  the  table  top,  and  is  attached 
to  one  of  the  binding  posts  of  the  block  C,  while  the 
positive  wire  is  attached  to  a  binding  post  at  the  end 
of  the  table  top,  and  from  here  it  passes  to  the  resist- 
ance frame  Ry  where  it  is  fixed  by  an  ordinary  metal- 
lic clamp. 

For  most  purposes  the  strength  of  current  need  not 
exceed  1—1.5  amperes  per  minute;  however,  it  may 
be  necessary  occasionally  to  increase  it  to  4  amperes 
per  minute.  Pyrite,  FeS2,  is  even  then  not  completely 


OXIDATIONS    BY    MEANS    OF    CURRENT.  113 

decomposed.  This  particular  case  requires  the  addi- 
tion of  a  quantity  of  cupric  oxide  equal  in  weight  to 
the  pyrite,  and  a  current  of  the  strength  last  indi- 
cated before  all  of  its  sulphur  is  fully  converted  into 
sulphuric  acid. 

By  increasing  the  number  of  crucibles  it  will  be 
possible  to  conduct  at  least  from  four  to  six  of  these 
decompositions  simultaneously,  and  by  using  a  volu- 
metric method  for  estimating  the  sulphuric  acid,  a 
sulphur  determination  can  easily  be  executed  in  forty 
minutes. 

Experience  has  demonstrated  that  0.1-0.2  gram  of 
material  will  require  about  20-25  grams  of  caustic 
potash. 

The  arsenic  in  minerals  is  rapidly  oxidized  to 
arsenic  acid  by  this  method. 

Chromite  also  seems  to  be  rapidly  decomposed 
when  subjected  to  this  treatment.  Several  quantita- 
tive experiments  have  been  carried  out,  and  the 
results  obtained  were  very  satisfactory. 


INDEX. 


AMPERE,  14 
i*     Amperemeter,  31 
Anions,  9 
Anode,  9 

Antimony,  determination  of,  87-89 
separation  from  arsenic,  102 

bismuth,  99 

copper,  92,  94 

lead,  99 

mercury,  98 

silver,  101 

tin,  102 
Arsenic,  determination  of,  89 

separation  from  antimony,  102 

bismuth,  99 

cadmium,  96 

copper,  92 

lead, 99 

mercury,  98 

silver,  101 

tin,  103 


D  ATTERY,  Bunsen,  19 
*-*    Crowfoot,  17 
Daniell,  17 
Grenet,  14 
Grove,  19 
Leclanche  16 
Meidinger,  17 
storage,  24 
Bismuth,  determination  of,  59-61 

separation  from  aluminium,  antimo- 
ny, arsenic,  cadmium,  chromium, 
cobalt,  iron,  manganese,  nickel, 
tin,  uranium,  zinc, 98-99 
separation  from  copper,  91 


CADMIUM,  determination  of,  54-57 
^   separation   from  aluminium,    anti- 
mony,  arsenic,   bismuth,  cobalt, 
iron,  manganese,  mercury,  nickel, 
silver,  tin,  uranium,  zinc,  94-97 
separation  from  copper,  90 

molybdenum  and  tungsten, 

108 
Cathions,  9 


Cathode,  9 

Cobalt,  determination  of,  72-75 
separation  from  bismuth,  99 

cadmium,  94,  95 

copper,  91 

iron,  105,  106 

manganese,  104 

mercury.  97,  98 

silver,  101 
Copper,  determination  of,  47-54 

separation  from  aluminium,  90,  91 

antimony,  92,  94 

arsenic,  93 

bismuth,  cobalt,  iron  lead, 
nickel,  uranium,  zinc,  91 

cadmium,  90 

manganese,  92 

mercury,  97 

silver,  100 

tin,  94 
Current,  action  upon  compounds,  10 


ELECTROLYSIS,  defined,  9 


"OLD,  determination  of,  85 


LJISTORICAL  account,  32-46 


IRON,  determination  of,  78-80 
separation  from  aluminium,  106 
bismuth,  99 
cadmium,  94 
cobalt,  105 
copper,  91 
lead,  99 

manganese,  103 
mercury,  97 
nickel,  105,  106 
silver,  64 
zinc,  105 


INDEX. 


EAD,  determination  of,  62-63 
'    separation  from  aluminium,  99 
antimony,  99 
arsenic,  99 
cadmium,  99 
cobalt,  99 
copper,  91,  99 
iron,  99 

mercury,  97,  99 
nickel,  99 
silver,  99,  100 
uranium,  99 
zinc,  99 


AGNETO-machines,  21 


M 

Manganese,  determination  of,  75-78 

separation  from  aluminium,  105,  106 
bismuth,  99 
cadmium,  94 
cobalt,  106 
copper,  92 
iron,  103,  105 
mercury,  97 
nickel,  106 
zinc,  106 
Mercury,  determination  of,  57-59 

separation    from    aluminium,    cad- 
mium, copper,  iron,  lead,  97 
antimony,  arsenic,  tin,  98 
from  cobalt,  nickel,  zinc,  97,  98 
molybdenum,  108 
palladium,  107 
tungsten,  108 
Molybdenum,  determination  of,  84 

separation  from  cadmium,  mercury 
and  silver,  108 


NICKEL,  determination  of,  72,  75 
separation  from  aluminium,  106 
bismuth,  99 
cadmium,  94 
cobalt,  94,  95 
copper,  91 
iron,  105,  106 
lead,  99 

manganese,  106 
mercury,  97,  98 
silver,  101 


OHM'  '.3 

^-s     Osmium,  37 

Oxidations  by  means  of  the  current,  108 


DALLADIUM,  determination  of,  83 

separation  from  mercury,  107 
Platinum,  determination  of,  82,  83 
Phosphoric  acid,  separation,  etc., 

103,  107 


R 


ESISTANCE  coils  and  frames, 

26,  27,  28 


SILVER,  determination  of,  63-67 
separation  from  aluminium,  copper, 
iron,  lead,  manganese,  uranium, 

100 
antimony,  arsenic,   cobalt, 

nickel,  tin,  zinc,  101 
cadmium,  94 

molybdenum  and  tungsten, 
1 08 
Sulphur,  oxidation  of,  108,  109 


'TANGENT  galvanometer,  30 

Thallium,  determination  of,  81 
Thermo-electric  pile,  21 
Tin,  determination  of,  85,  86 

separation  from  antimony,  102 

arsenic,  103 

bismuth,  99 

cadmium,  96 

copper,  94 

lead, 99 

mercury,  98 


U 


RANIUM,  determination  of,  80 


fOLT,  14 

Voltameter,  29 


'7INC,  determination  of,  67-72 
^     separation  from  aluminium,  106 
bismuth,  99 
cadmium,  94,  95,  96 
copper,  91 
iron,  105 
lead,  99 

manganese,  106 
mercury,  97,  98 
silver,  101 


JUST    PUBLISHED. 


FUEL  AND  ITS  APPLICATIONS, 

BY  E.  J.  MILLS,  D.SC.,F.R.*.,  AND  F.  J.  ROWAN,  C.E.,  ASSISTED 
BY  OTHERS,  INCLUDING  MR.  F.  P.  DEWEY,  OF  THE 
SMITHSONIAN  INSTITUTE,  WASHINGTON,  D.  C. 


7  PLATES  AND  607  OTHER  ILLUSTRATIONS. 

ROYAL  OCTAVO,  PAGES,  xx  +  802.     HANDSOME  CLOTH,  $7.50. 
HALF  MOROCCO,  $9.00. 

BEING   THE    FIRST    OF   A    SERIES    OF    WORKS    ON 

CHEMICAL   TECHNOLOGY;   OR,  CHEMISTRY  IN  ITS 

APPLICATION  TO  ARTS  AND  MANUFACTURES.     EDITED  BY 
CHARLES  EDWARD  GROVES,  F.R.C.,  AND  WILLIAM  THORP,  B.SC. 


There  is  no  other  item  of  expense  that  enters  more  largely 
into  the  cost  of  producing  than  that  of  Fuel.  The  importance, 
therefore,  of  being  acquainted  with  the  latest  and  most  economi- 
cal methods  of  using  and  applying  it  is  apparent,  and  in  no 
other  branch  of  manufacturing  has  there  been  greater  advance- 
ment made  than  in  our  knowledge  of  combustion,  and  the 
economical  distribution  and  utilization  of  heat. 

The  work  has  been  prepared  with  great  care,  so  that  every- 
thing of  value  pertaining  to  the  subject  might  receive  proper 
treatment.  It  appeals  generally  to  all  interested  in  the  use  of 


[OVER.] 


P.  BLAKISTON,  SON  &  CO.,  Scientific  and  Medical  Publishers, 
1012  "Walnut  Street,  Philadelphia. 


MILLS  ON  FUEL  AND  ITS  APPLICATIONS. 


From  The  American  Gas- Light  Journal. 

"  Even  a  hasty  glance  through  the  volume  before  us  compels  the  ver- 
dict that  the  editors  and  compilers  have  most  satisfactorily  carried  out 
their  purposes,  and  we  have  no  hesitation  in  advising  the  gas  men  to 
purchase  the  book.  It  contains  no  less  than  seven  handsome  plates,  and 
607  separate  illustrations ;  the  letter-press  and  engravings,  with  index 
(which  is  most  copious),  take  up  802  pages,  and  within  that  compass 
the  story  of  '  Fuel  and  Its  Application '  is  amply  and  well  told.  Space 
forbids  any  lengthy  review  of  the  volume,  but  we  can  say  that  its  pages 
teem  with  information  for  the  gas  maker." 

From  Engineering  and  Mining  Journal ,  New  York. 

"  The  authors  appear  to  realize  the  difficulty  of  their  undertaking  when 
they  say :  '  The  law  of  progress,  to  which  all  industrial  processes  are 
subject,  however,  causes  any  work  on  technology  to  become  out  of  date 
in  a  few  years,  and  this  applies  in  a  special  manner  to  the  very  large 
class  of  operations  which  are  closely  connected  with  chemistry.  For 
nowhere  has  the  extraordinary  activity  in  all  departments  of  knowledge 
which  has  been  witnessed  during  the  last  thirty  years  been  more  marked 
than  in  the  domain  of  chemistry,  and  this  has  necessarily  borne  fruit,  not 
only  in  the  modification  of  old  methods,  but  also  in  the  invention  of  new 
processes,  and  in  the  introduction  of  more  perfect  methods  of  research.' 

"  The  book  will  be  very  useful  for  reference,  and  should  be  of  especial 
value  to  the  inventors  and  experimenters  or  users  of  processes  or  appli- 
ances for  the  combustion  of  fuels,  since  in  it  can  be  found  a  record  of  a 
large  part  of  the  methods  heretofore  proposed  and  adopted.  Where 
critical  remarks  are  made  they  appear  to  be  judicious.  The  illustrations 
are  very  numerous  and  are  well  selected.  An  immense  amount  of 
information  has  been  crowded  into  these  closely  printed  802  pages." 

From  The  "Railroad  and  Engineering  Journal. 

"  The  first  volume,  on  Fuel,  is  naturally  one  of  the  most  important  and 
practical  in  its  direct  applications.  It  contains  chapters  on  Wood,  on 
Peat,  on  Charcoal,  on  Coal,  on  Coke,  on  Artificial  Fuel,  on  Liquid  Fuel, 
on  Gaseous  Fuels,  on  the  Different  Applications  of  Fuel,  on  Ovens,  on 
Furnaces,  etc.,  etc.  Great  pains  have  been  taken  to  collect  information 
from  all  possible  sources,  and  to  include  the  results  not  only  of  experi- 
ments, but  of  practical  working  in  a  number  of  different  directions. 

"  The  book  is  very  fully  illustrated,  a?,  indeed,  the  nature  of  the  sub- 
ject requires,  and  includes  a  large  number  of  tables  giving  fuel  statistics, 
analyses  of  different  fuels,  and  comparative  results.  It  has,  what  every 
book  of  the  kind  should,  but  does  not  always  have,  a  very  full  index." 


P.  BLAKISTON,  SON  &  CO.,  Scientific  and  Medical  Publishers, 
1012  Walnut   Street,  Philadelphia. 


CATALOGUE  No.  7. 


JULY,  1890. 


A  CATALOGUE 

OF 

BOOKS  FOR  STUDENTS. 


INCLUDING   THE 


PQUIZ-COMPENDS? 


CONTENTS. 


>4>5 

Obstetrics.     .                              10 

Pathology,  Histology, 

II 

ii 

Pharmacy,     . 

12 

6 

Physiology,  . 
Practice  of  Medicine, 

II 
12 

g 

Prescription  Books, 

12 

8 

?  Quiz-Compends  ? 
Skin  Diseases, 

14,  15 

.    12 

9 

10 

Therapeutics,         .         .         .9 

9 
9 

Urine  and  Urinary  Organs,     13 
Venereal  Diseases,        .         .13. 

10 

New  Series  of  Manuals,  2,3,4 

Anatomy, 

Biology, 

Chemistry,     . 

Children's  Diseases, 

Dentistry, 

Dictionaries, 

Eye  Diseases, 

Electricity,    . 

Gynaecology, 

Hygiene, 

Materia  Medica, 

Medical  Jurisprudence 


PUBLISHED   BY 

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"An  excellent  Series  of  Manuals." — Archives  of  Gyncecology. 

A  NEW  SERIES  OF 

STUDENTS'    MANUALS 

On  the  various  Branches  of  Medicine  and  Surgery. 

Can  be  used  by  Students  of  any  College. 
Price  of  each,  Handsome  Cloth,  $3.00.    Full  Leather,  $3.50. 

The  object  of  this  series  is  to  furnish  good  manuals 
for  the  medical  student,  that  will  strike  the  medium 
between  the  compend  on  one  hand  and  the  prolix  text- 
book on  the  other — to  contain  all  that  is  necessary  for 
the  student,  without  embarrassing  him  with  a  flood  of 
theory  and  involved  statements.  They  have  been  pre- 
pared by  well-known  men,  who  have  had  large  experience 
as  teachers  and  writers,  and  who  are,  therefore,  well 
informed  as  to  the  needs  of  the  student. 

Their  mechanical  execution  is  of  the  best — good  type 
and  paper,  handsomely  illustrated  whenever  illustrations 
are  of  use,  and  strongly  bound  in  uniform  style. 

Each  book  is  sold  separately  at  a  remarkably  low 
price,  and  the  immediate  success  of  several  of  the 
volumes  shows  that  the  •  series  has  met  with  popular 
favor. 

No.  1.     SURGERY.    236  Illustrations. 
A    Manual   of    the    Practice  of    Surgery.     By  WM.  J. 

WALSHAM,  M.D.,  Asst.  Surg.  to,  and  Demonstrator  of 

Surg.   in,  St.   Bartholomew's  Hospital,   London,   etc. 

228  Illustrations. 

Presents  the  introductory  facts  in  Surgery  in  clear,  precise 
language,  and  contains  all  the  latest  advances  in  Pathology, 
Antiseptics,  etc. 

"  It  aims  to  occupy  a  position  midway  between  the  pretentious 
manual  and  the  cumbersome  System  of  Surgery,  and  its  general 
character  may  be  summed  up  in  one  word — practical." — The  Medi- 
cal Bulletin. 

"  Walsham,  besides  being  an  excellent  surgeon,  is  a  teacher  in 
its  best  sense,  and  having  had  very  great  experience  in  the 
preparation  of  candidates  for  examination,  and  their  subsequent 
professional  career,  may  be  relied  upon  to  have  carried  out  his 
work  successfully.  Without  following  out  in  detail  his  arrange- 
ment, which  is  excellent,  we  can  at  once  say  that  his  book  is  an 
embodiment  of  modern  ideas  neatly  strung  together,  with  an  amount 
of  careful  organization  well  suited  to  the  candidate,  and,  indeed,  to 
the  practitioner." — British  Medical  Journal. 

Price  of  each  Book,  Cloth,  $3.00  ;  Leather,  $3.50. 


THE  NEW  SERIES  OF  MANUALS. 


No.  2.    DISEASES  OP  WOMEN.    15O  Illus. 

NEW    EDITION. 

The  Diseases  of  Women.  Including  Diseases  of  the 
Bladder  and  Urethra.  By  DR.  F.  WINCKEL,  Professor 
of  Gynaecology  and  Director  of  the  Royal  University 
Clinic  for  Women,  in  Munich.  Second  Edition.  Re- 
vised and  Edited  by  Theophilus  Parvin,  M.D., 
Professor  of  Obstetrics  and  Diseases  of  Women  and 
Children  in  Jefferson  Medical  College.  150  Engrav- 
ings, most  of  which  are  original. 
"  The  book  will  be  a  valuable  one  to  physicians,  and  a  safe  and 

satisfactory  one  to  put  into  the  hands  of  students.    It  is  issued  in  a 

neat  and  attractive  form,  and  at  a  very  reasonable  price." — Boston 

Medical  and  Surgical  Journal. 

No.  3.    OBSTETRICS.    227  Illustrations. 
A  Manual  of  Midwifery.     By  ALFRED  LEWIS  GALABIN, 
M.A.,  M.D.,  Obstetric  Physician  and  Lecturer  on  Mid- 
wifery and  the  Diseases  of  Women  at  Guy's  Hospital, 
London;     Examiner   in    Midwifery   to   the    Conjoint 
Examining  Board  of  England,  etc.     With  227  Illus. 
"  This  manual  is  one  we  can  strongly  recommend  to   all  who 
desire  to  study  the  science  as  well  as  the  practice  of  midwifery. 
Students   at  the  present  time  not  only  are  expected  to  know  the 
principles  of  diagnosis,  and  the  treatment  of  the  various  emergen- 
cies and  complications  that  occur  in  the  practice  of  midwifery,  but 
find  that  the  tendency  is  for  examiners  to  ask  more  questions 
relating  to  the  science  of  the  subject  than  was  the  custom  a  few 
years   ago.  *  *  *    The  general  standard  of  the  manual  is  high  ; 
and  wherever  the  science  and  practice  of  midwifery  are  well  taught 
it  will  be  regarded  as  one  of  the  most  important  text-books  on  the 
subject" — London  Practitioner. 

No.  4.    PHYSIOLOGY.    Fourth  Edition. 

321  ILLUSTRATIONS  AND  A  GLOSSARY. 
A  Manual  of  Physiology.  By  GERALD  F.  YEO,  M.D., 
F.R.C.S.,  Professor  of  Physiology  in  King's  College, 
London.  321  Illustrations  and  a  Glossary  of  Terms. 
Fourth  American  from  second  English  Edition,  revised 
and  improved.  758  pages. 

This  volume  was  specially  prepared  to  furnish  students  with  a 
new  text-book  of  Physiology,  elementary  so  far  as  to  avoid  theories 
which  have  not  borne  the  test  of  time  and  such  details  of  methods 
as  are  unnecessary  for  students  in  our  medical  colleges. 

"  The  brief  examination  I  have  given  it  was  so  favorable  that  I 

B'aced  it  in  the  list  of  text-books  recommended  in  the  circular  of  the 
niversity   Medical    College."— Prof.    Lewis  A.   Stimson,   M.D., 
3^  East  33d  Street,  New  York. 

Price  of  each  Book,  Cloth,  $3.00;  Leather,  $3.50. 


THE  NEW  SERIES  OF  MANUALS. 


No.  5.    ORGANIC  CHEMISTRY. 

Or  the  Chemistry  of  the  Carbon  Compounds.  By  Prof. 
VICTOR  VON  RICHTER,  University  of  Breslau.  Au- 
thorized translation,  from  the  Fourth  German  Edition. 
By  EDGAR  F.  SMITH,  M.A.,  PH.D.  ;  Prof,  of  Chemistry 
in  University  of  Pennsylvania;  Member  of  the  Chem. 
Socs.  of  Berlin  and  Paris. 

"  I  must  say  that  this  standard  treatise  is  here  presented  in  a 
remarkably  compendious  shape."— y.  W.  Holland,  M.D.,  Professor 
of  Chemistry,  Jefferson  Medical  College,  Philadelphia. 

"  This  work  brings  the  whole  matter,  in  simple,  plain  language, 
to  the  student  in  a  clear,  comprehensive  manner.  The  whole 
method  of  the  work  is  one  that  is  more  readily  grasped  than  that  of 
older  and  more  famed  text-books,  and  we  look  forward  to  the  time 
when,  to  a  great  extent,  this  work  will  supersede  others,  on  the 
score  of  its  better  adaptation  to  the  wants  of  both  teacher  and 
student." — Pharmaceutical  Record. 

"  Prof,  von  Richter's  work  has  the  merit  of  being  singularly 
clear,  well  arranged,  and  for  its  bulk,  comprehensive.  Hence,  it 
will,  as  we  find  it  intimated  in  the  preface,  prove  useful  not  merely 
as  a  text-book,  but  as  a  manual  of  reference." — The  Chemical 
News,  London. 

No.  6.    DISEASES  OP  CHILDREN. 

SECOND  EDITION. 

A  Manual.  By  J.  F.  GOODHART,  M.D.,  Phys.  to  the 
Evelina  Hospital  for  Children ;  Asst.  Phys.  to 
Guy's  Hospital,  London.  Second  American  Edition. 
Edited  and  Rearranged  by  Louis  STARR,  M.D.,  Clinical 
Prof,  of  Dis.  of  Children  in  the  Hospital  of  the  Univ. 
of  Pennsylvania,  and  Physician  to  the  Children's  Hos- 
pital, Phila.  Containing  many  new  Prescriptions,  a  list 
of  over  50  Formulae,  conforming  to  the  U.  S.  Pharma- 
copoeia, and  Directions  for  making  Artificial  Human 
Milk,  for  the  Artificial  Digestion  of  Milk,  etc.  Illus. 

"  The  author  has  avoided  the  not  uncommon  error  of  writing  a 
book  on  general  medicine  and  labeling  it  '  Diseases  of  Children,' 
but  has  steadily  kept  in  view  the  diseases  which  seemed  to  be 
incidental  to  childhood,  or  such  points  in  disease  as  appear  to  be  so 
peculiar  to  or  pronounced  in  children  as  to  justify  insistence  upon 
them.  *  *  *  A  safe  and  reliable  guide,  and  in  many  ways 
admirably  adapted  to  the  wants  of  the  student  and  practitioner." — 
American  Journal  of  Medical  Science. 

Price  of  each  Book.  Cloth,  $3.00  ;  Leather,  $3.50. 


THE  NEW  SERIES  OF  MANUALS. 


No.  6.     Goodhart  and  Starr  : — Continued. 

"  Thoroughly  individual,  original  and  earnest,  the  work  evi- 
dently of  a  close  observer  and  an  independent  thinker,  this  book, 
though  small,  as  a  handbook  or  compendium  is  by  no  means  made 
up  of  bare  outlines  or  standard  facts." — The  Therapeutic  Ga- 
zette. 

"  As  it  is  said  of  some  men,  so  it  might  be  said  of  some  books, 
that  they  are  'born  to  greatness.'  This  new  volume  has,  we 
believe,  a  mission,  particularly  in  the  hands  of  the  younger 
members  of  the  profession.  In  these  days  of  prolixity  in  medical 
literature,  it  is  refreshing  to  meet  with  an  author  who  knows  both 
what  to  say  and  when  he  has  said  it.  The  work  of  Dr.  Goodhart 
(admirably  conformed,  by  Dr.  Starr,  to  meet  American  require- 
ments) is  the  nearest  approach  to  clinical  teaching  without  the 
actual  presence  of  clinical  material  that  we  have  yet  seen." — New 
York  Medical  Record. 

No.  7.    PRACTICAL  THERAPEUTICS. 

FOURTH  EDITION,  WITH  AN  INDEX  OF  DISEASES. 

Practical  Therapeutics,  considered  with  reference  to 
Articles  of  the  Materia  Medica.  Containing,  also,  an 
Index  of  Diseases,  with  a  list  of  the  Medicines 
applicable  as  Remedies.  By  EDWARD  JOHN  WARING, 
M.D.,  F.R.C.P.  Fourth  Edition.  Rewritten  and  Re- 
vised by  DUDLEY  W.  BUXTON,  M.D.,  Asst.  to  the  Prof, 
of  Medicine  at  University  College  Hospital. 

"  We  wish  a  copy  could  be  put  in  the  hands  of  every  Student  or 
Practitioner  in  the  country.  In  our  estimation,  it  is  the  best  book 
of  the  kind  ever  written.  '—N.  Y.  Medical  Journal. 

No.  8.    MEDICAL  JURISPRUDENCE  AND 
TOXICOLOGY. 

NEW,  REVISED  AND  ENLARGED  EDITION. 

By  John  J.  Reese,  M.D.,  Professor  of  Medical  Jurispru- 
dence and  Toxicology  in  the  University  of  Pennsyl- 
vania ;  President  of  the  Medical  Jurisprudence  Society 
of  Phila. ;  2d  Edition,  Revised  and  Enlarged. 

"  This  admirable  text-book."— Amer.Jour.  of  Med.  Sciences. 

"  We  lay  this  volume  aside,  after  a  careful  perusal  of  its  pages, 
with  the  profound  impression  that  it  should  be  in  the  hands  of  every 

doctor  and  lawyer.  It  fully  meets  the  wants  of  all  students 

He  has  succeeded  in  admirably  condensing  into  a  handy  volume  all 
the  essential  points." — Cincinnati  Lancet  and  Clinic. 

Price  of  each  Book,  Cloth,  $3,00 ;  Leather,  $3.50. 


6          STUDENTS'  TEXT-BOOKS  AND  MANUALS. 

ANATOMY. 

Macalister's  Human  Anatomy.  816  Illustrations.  A  new 
Text-book  for  Students  and  Practitioners,  Systematic  and  Topo- 
graphical, including  the  Embryology,  Histology  and  Morphology 
of  Man.  With  special  reference  to  the  requirements  of 
Practical  Surgery  and  Medicine.  With  816  Illustrations, 
400  of  which  are  original.  Octavo.  Cloth,  7.50;  Leather,  8.50 

Ballou's  Veterinary  Anatomy  and  Physiology.  Illustrated. 
By  Wm.  R.  Ballou,  M.D.,  Professor  of  Equine  Anatomy  at  New 
York  College  of  Veterinary  Surgeons.  29  graphic  Illustrations. 
I2mo.  Cloth,  i.oo;  Interleaved  for  notes,  1.25 

Holden's  Anatomy.  A  manual  of  Dissection  of  the  Human 
Body.  Fifth  Edition.  Enlarged,  with  Marginal  References  and 
over  200  Illustrations.  Octavo.  Cloth,  5.00;  Leather,  &oo 

Bound  in  Oilcloth,  for  the  Dissecting  Room,  $4.50. 

"  No  student  of  Anatomy  can  take  up  this  book  without  being 
pleased  and  instructed.  Its  Diagrams  are  original,  striking  and 
suggestive,  giving  more  at  a  glance  than  pages  of  text  description. 
*  *  *  The  text  matches  the  illustrations  in  directness  of  prac- 
tical application  and  clearness  of  detail." — Ne^v  York  Medical 
Record. 

Holden's  Human  Osteology.  Comprising  a  Description  of  the 
Bones,  with  Colored  Delineations  of  the  Attachments  of  the 
Muscles.  The  General  and  Microscopical  Structure  of  Bone  and 
its  Development.  With  Lithographic  Plates  and  Numerous  Illus- 
trations. Seventh  Edition.  8vo.  Cloth,  6.00 

Holden's  Landmarks,  Medical  and  Surgical.   4th  ed.   Clo.,  1.25 

Heath's  Practical  Anatomy.  Sixth  London  Edition.  24  Col- 
ored Plates,  and  nearly  300  other  Illustrations.  Cloth,  5.00 

Potter's  Compend  of  Anatomy.  Fourth  Edition.  117  Illus- 
trations. Cloth,  i.oo;  Interleaved  for  Notes,  1.25 

CHEMISTRY. 

Bartley's  Medical  Chemistry.  Second  Edition.  A  text-book 
prepared  specially  for  Medical,  Pharmaceutical  and  Dental  Stu- 
dents. With  50  Illustrations,  Plate  of  Absorption  Spectra  and 
Glossary  of  Chemical  Terms.  Revised  and  Enlarged.  Cloth,  2. 50 

Trimble.  Practical  and  Analytical  Chemistry.  A  Course  in 
Chemical  Analysis,  by  Henry  Trimble,  Prof,  of  Analytical  Chem- 
istry in  the  Phila.  College  of  Pharmacy.  Illustrated.  Third 
Edition.  8vo.  Cloth,  1.50 

JH&"  See  pages  2  to  j  for  list  of  Students'  Manuals. 


STUDENTS'  TEXT-BOOKS  AND  MANUALS.         7 

Chemistry  :— Continued. 

Bloxam's  Chemistry,  Inorganic  and  Organic,  with  Experiments. 
Seventh  Edition.  Enlarged  and  Rewritten.  330  Illustrations* 

Cloth,  4.50 ;  Leather,  5.50 

Richter's  Inorganic  Chemistry.  A  text-book  for  Students. 
Third  American,  from  Fifth  German  Edition.  Translated  by 
Prof.  Edgar  F.  Smith,  PH.D.  89  Wood  Engravings  and  Colored 
Plate  of  Spectra.  Cloth,  2.00 

Richter's  Organic  Chemistry,  or  Chemistry  of  the  Carbon 
Compounds.  Illustrated.  Cloth,  3.00  ;  Leather,  3.50 

Symonds.  Manual  of  Chemistry,  for  the  special  use  of  Medi- 
cal Students.  By  BKANDRKTH  SYMONDS,  A.M.,  M.D.,  Asst. 
Physician  Roosevelt  Hospital,  Out- Patient  Department;  Attend- 
ing Physician  Northwestern  Dispensary,  New  York.  i2mo. 

Cloth,  2.00 ;  Interleaved  for  Notes,  2.40 

Tidy.     Modern  Chemistry,    ad  Ed.  Cloth,  5.50 

Leffmann's  Compend  of  Chemistry.  Inorganic  and  Organic. 
Including  Urinary  Analysis  and  the  Sanitary  Examination  of 
Water.  New  Edition.  Cloth,  i.oo;  Interleaved  for  Notes,  1.25 

Muter.  Practical  and  Analytical  Chemistry.  Second  Edi- 
tion. Revised  and  Illustrated.  Cloth,  2.00 

Holland.  The  Urine,  Common  Poisons,  and  Milk  Analysis, 
Chemical  and  Microscopical.  For  Laboratory  Use.  3d 
Edition,  Enlarged.  Illustrated.  Cloth,  i.oo 

Van  Niiys.     Urine  Analysis.     Illus.  Cloth,  2.00 

Wolff 's  Applied  Medical  Chemistry.  By  Lawrence  Wolff, 
M.D.,Dem.  of  Chemistry  in  Jefferson  Medical  College.  Clo.,i.oo 

CHILDREN. 

Goodhart  and  Starr.  The  Diseases  of  Children.  Second 
Edition.  By  T.  F.  Goodhart,  M.D.,  Physician  to  the  Evelina 
Hospital  for  Children ;  Assistant  Physician  to  Guy's  Hospital, 
London.  Revised  and  Edited  by  Louis  Starr,  M.D.,  Clinical 
Professor  of  Diseases  of  Children  in  the  Hospital  of  the  Univer- 
sity of  Pennsylvania;  Physician  to  the  Children's  Hospital, 
Philadelphia.  Containing  many  Prescriptions  and  Formulae, 
conforming  to  the  U.  S.  Pharmacopoeia,  Directions  for  making 
Artificial  Human  Milk,  for  the  Artificial  Digestion  of  Milk,  etc. 
Illustrated.  Cloth,  3.00;  Leather,  3.50 

Hatfield.  Diseases  of  Children.  By  M.  P.  Hatfield,  M.D., 
Professor  of  Diseases  of  Children,  Chicago  Medical  College. 
i2mo.  Cloth,  i.oo;  Interleaved,  1.25 

Day.  On  Children.  A  Practical  and  Systematic  Treatise. 
Second  Edition.  8vo.  752  pages.  Cloth,  3.00;  Leather,  4.00 

9&~  See  pages  14  and  rf  for  list  of  f  Quiz-  Compends  f 


8          STUDENTS'  TEXT-BOOKS  AND  MANUALS. 

Children: —  Continued. 

Meigs  and  Pepper.  The  Diseases  of  Children.  Seventh 
Edition.  8vo.  Cloth,  5.00;  Leather,  6.00 

Starr.  Diseases  of  the  Digestive  Organs  in  Infancy  and 
Childhood.  With  chapters  on  the  Investigation  of  Disease, 
and  on  the  General  Management  of  Children.  By  Louis  Starr, 
M.D.,  Clinical  Professor  of  Diseases  of  Children  in  the  Univer- 
sity of  Pennsylvania;  with  a  section  on  Feeding,  including  special 
Diet  Lists,  etc.  Illus.  Cloth,  2.50 

DENTISTRY. 

Fillebrown.    Operative  Dentistry.    330  Illus.          Cloth,  2.50 

Flagg's  Plastics  and  Plastic  Filling.     3d  Ed.         Preparing. 

Gorgas.  Dental  Medicine.  A  Manual  of  Materia  Medica  and 
Therapeutics.  Third  Edition.  Cloth,  3.50 

Harris.  Principles  and  Practice  of  Dentistry.  Including 
Anatomy,  Physiology,  Pathology,  Therapeutics,  Dental  Surgery 
and  Mechanism.  Twelfth  Edition.  Revised  and  enlarged  by 
Professor  Gorgas.  1028  Illustrations.  Cloth,  7.00  ;  Leather,  8.00 

Richardson's  Mechanical  Dentistry.  Fifth  Edition.  569 
Illustrations.  8vo.  Cloth,  4.50;  Leather,  5.50 

Stocken's  Dental  Materia  Medica.  Third  Edition.  Cloth,  2.50 

Taft's  Operative  Dentistry.  Dental  Students  and  Practitioners. 
Fourth  Edition,  too  Illustrations.  Cloth,  4.25  ;  Leather,  5.00 

Talbot.  Irregularities  of  the  Teeth,  and  their  Treatment. 
Illustrated.  8vo.  Cloth,  1.50 

Tomes'  Dental  Anatomy.     Third  Ed.     191  Illus.      Cloth,  4.00 

Tomes'  Dental  Surgery.  3d  Edition.  Revised.  292  Illus. 
772  Pages.  Cloth,  5.00 

DICTIONARIES. 

Gould's  New  Medical  Dictionary.  Containing  the  Definition 
and  Pronunciation  of  all  words  in  Medicine,  with  many  useful 
Tables  etc.  ^  Dark  Leather,  3.25  ;  ^  Mor.,  Thumb  Index  4.25 
See  last  page. 

Cleaveland's  Pocket  Medical  Lexicon.    3ist  Edition.    Giving 

correct  Pronunciation  and  Definition.     Very  small  pocket  size. 

Cloth,  red  edges  .75  ;  pocket-book  style,  i.oo 

Longley's  Pocket  Dictionary.  The  Student's  Medical  Lexicon, 
giving  Definition  and  Pronunciation  of  all  Terms  used  in  Medi- 
cine, with  an  Appendix  giving  Poisons  and  Their  Antidotes, 
Abbreviations  used  in  Prescriptions,  Metric  Scale  of  Doses,  etc. 
24010.  Cloth,  i.oo;  pocket-book  style,  1.25 

KiT  See  pages  2  to  5  for  list  of  Students'  Manuals. 


STUDENTS'  TEXT-BOOKS  AND  MANUALS.          9 

EYE. 

Arlt.  Diseases  of  the  Eye.  Including  those  of  the  Conjunc- 
tiva, Cornea,  Sclerotic,  Iris  and  Ciliary  Body.  By  Prof.  Von 
Arlt.  Translated  by  Dr.  Lyman  Ware.  Illus.  8vo.  Cloth,  2.50 

Hartridge  on  Refraction.    4th  Ed.  Cloth,  2.00 

Meyer.  Diseases  of  the  Eye.  A  complete  Manual  for  Stu- 
dents and  Physicians.  270  Illustrations  and  two  Colored  Plates. 
8vo.  Cloth,  4.50;  Leather,  5.50 

Fox  and  Gould.  Compend  of  Diseases  of  the  Eye  and 
Refraction.  2d  Ed.  Enlarged.  71  Illus.  39  Formulae. 

Cloth,  i. oo  ;  Interleaved  for  Notes,  1.25 

ELECTRICITY. 

Mason's  Compend  of  Medical  and  Surgical  Electricity. 
With  numerous  Illustrations.  12010.  Cloth,  i.oo 

HYGIENE. 

Parkes'  (Ed.  A.)  Practical  Hygiene.  Seventh  Edition,  en- 
larged. Illustrated.  8vo.  Cloth,  4.50 

Parkes1  (L.  C.)  Manual  of  Hygiene  and  Public  Health. 
i2mo.  '  Cloth,  2.50 

Wilson's  Handbook  of  Hygiene  and  Sanitary  Science. 
Sixth  Edition.  Revised  and  Illustrated.  Cloth,  2.75 

MATERIA  MEDICA  AND  THERAPEUTICS. 

Potter's  Compend  of  Materia  Medica,  Therapeutics  and 

Prescription  'Writing.     Fifth  Edition,  revised  and  improved. 

Cloth,  i.oo;  Interleaved  for  Notes,  1.25 

Biddle's  Materia  Medica.  Eleventh  Edition.  By  the  late 
John  B.  Biddle,  M.D.,  Professor  of  Materia  Medica  in  Jefferson 
Medical  College,  Philadelphia.  Revised,  and  rewritten,  by 
Clement  Biddle,  M.D.,  Assist.  Surgeon,  U.  S.  N.,  assisted  by 
Henry  Morris,  M.D.  8vo.,  illustrated.  Cloth,  4.25;  Leather,  5.00 

Headland's  Action  of  Medicines.    9th  Ed.    8vo.     Cloth,  3.00 

Potter.  Materia  Medica,  Pharmacy  and  Therapeutics. 
Including  Action  of  Medicines,  Special  Therapeutics,  Pharma- 
cology, etc.  Second  Edition.  Cloth,  4.00 ;  Leather,  5,00 

Starr,  Walker  and  Powell.  Synopsis  of  Physiological 
Action  of  Medicines, based  upon  Prof.  H.  C.  Wood's  "  Materia 
Medica  and  Therapeutics."  3d  Ed.  Enlarged.  Cloth,  .75 

"Waring.  Therapeutics.  With  an  Index  of  Diseases  and 
Remedies.  4th  Edition.  Revised.  Cloth,  3.00;  Leather,  3.50 
4&-  See  pages  14  and  ij  for  list  of  f  Quit-  Compends  f 


10        STUDENTS'  TEXT-BOOKS  AND  MANUALS. 

MEDICAL  JURISPRUDENCE. 
Reese.    A  Text-book  of  Medical  Jurisprudence  and  Toxi- 
cology.    By  John  J.  Reese,  M.D.,  Professor  of  Medical  Juris- 
prudence   and  Toxicology  in  the  Medical  Department  of  the 
University    of  Pennsylvania ;     President  of  the  Medical  Juris- 

B-udence  Society  of  Philadelphia;    Physician  to  St.  Joseph's 
ospital ;   Corresponding  Member  of  The  New  York  Medico- 
legal  Society.     2d  Edition.  Cloth,  3.00;  Leather,  3.50 
Woodman  and  Tidy's   Medical  Jurisprudence  and  Toxi- 
cology.   Chromo-Lithographic  Plates  and  116  Wood  engravings. 

Cloth,  7.50;  Leather,  8.50 

OBSTETRICS  AND  GYNAECOLOGY. 

Byford.  Diseases  of  Women.  The  Practice  of  Medicine  and 
Surgery,  as  applied  to  the  Diseases  and  Accidents  Incident  to 
Women.  By  W.  H.  Byford,  A.M.,  M.D.,  Professor  of  Gynaecology 
in  Rush  Medical  College  and  of  Obstetrics  in  the  Woman's  Med- 
ical College,  etc.,  and  Henry  T.  Byford,  M.D.,  Surgeon  to  the 
Woman's  Hospital  of  Chicago  ;  Gynaecologist  to  St.  Luke's 
Hospital,  etc.  Fourth  Edition.  Revised,  Rewritten  and  En- 
larged. With  306  Illustrations,  over  100  of  which  are  original. 
Octavo.  832  pages.  Cloth,  5.00  ;  Leather,  6.00 

Cazeaux  and  Tarnier's  Midwifery.  With  Appendix,  by 
Munde.  The  Theory  and  Practice  of  Obstetrics  ;  including  the 
Diseases  of  Pregnancy  and  Parturition,  Obstetrical  Operations, 
etc.  By  P.  Cazeaux.  Remodeled  and  rearranged,  with  revi- 
sions and  additions,  by  S.  Tarnier,  M.D.,  Professor  of  Obstetrics 
and  Diseases  of  Women  and  Children  in  the  Faculty  of  Medicine 
of  Paris.  Eighth  American,  from  the  Eighth  French  and  First 
Italian  Edition.  Edited  by  Robert  J.  Hess,  M.D.,  Physician  to 
the  Northern  Dispensary,  Philadelphia,  with  an  appendix  by 
Paul  F.  Munde,  M.D.,  Professor  of  Gynaecology  at  the  N.  Y. 
Polyclinic.  Illustrated  by  Chromo-Lithographs,  Lithographs, 
and  other  Full-page  Plates,  seven  of  which  are  beautifully  colored, 
and  numerous  Wood  Engravings.  Students'  Edition.  One 
Vol.,  8vo.  Cloth,  5.00;  Leather,  6.00 

Lewers'  Diseases  of  Women.  A  Practical  Text-Book.  139 
Illustrations.  Second  Edition.  Cloth,  2.50 

Parvin's  Winckel's  Diseases  of  Women.  Second  Edition. 
Including  a  Section  on  Diseases  of  the  Bladder  and  Urethra. 
150  Illustrations.  Revised.  See  page  3. 

Cloth,  3.00;  Leather,  3.50 

Morris.    Compend  of  Gynaecology.     Illustrated.      In  Press. 

Winckel's  Obstetrics.  A  Text-book  on  Midwifery,  includ- 
ing the  Diseases  of  Childbed.  By  Dr.  F.  Winckel,  Professor 
of  Gynsecology,  and  Director  of  the  Royal  University  Clinic  for 
Women,  in  Munich.  Authorized  Translation,  by  J.  Clifton 
Edgar,  M.D.,  Lecturer  on  Obstetrics,  University  Medical  Col- 
lege, New  York,  with  nearly  200  handsome  illustrations,  the 
majority  of  which  are  original  with  this  work.  Octavo. 

Cloth,  6.00;   Leather,  7.00 

Landis'  Compend  of  Obstetrics.  Illustrated.  4th  edition, 
enlarged.  Cloth,  i.oo;  Interleaved  for  Notes,  1.25 

t  Pages  2  to  3  for  list  of  New  Manuals. 


STUDENTS'   TEXT-BOOKS  AND  MANUALS.         11 

Obstetrics  and  Gynacology  :—  Continued. 

Galabin's  Midwifery.  By  A.  Lewis  Galabin,  M.D.,  F.K.C.P. 
227  Illustrations.  Seepages.  Cloth,  3.00;  Leather,  3.50 

Glisan's  Modern  Midwifery.    2d  Edition.  Cloth,  3.00 

Rigby's  Obstetric  Memoranda.    4th  Edition.  Cloth,  .50 

Meadows'  Manual  of   Midwifery.     Including  the  Signs  and 

Symptoms  of  Pregnancy,  Obstetric  Operations,  Diseases  of  the 

Puerperal  State,  etc.     145  Illustrations.    494  pages.    Cloth,  2.00 

Swayne's   Obstetric   Aphorisms.      For  the  use  of  Students 

commencing  Midwifery  Practice.     8th  Ed.     12010.      Cloth,  1.25 

PATHOLOGY.    HISTOLOGY.    BIOLOGY. 

Bowlby.  Surgical  Pathology  and  Morbid  Anatomy,  for 
Students.  135  Illustrations.  i2mo.  Cloth,  2.00 

Davis'  Elementary  Biology.     Illustrated.  Cloth,  4.00 

Gilliam's  Essentials  of  Pathology.  A  Handbook  for  Students. 
47  Illustrations.  i2mo.  Cloth,  2.00 

***  The  object  of  this  book  is  to  unfold  to  the  beginner  the  funda- 

mentals of  pathology  in  a  plain,  practical  way,  and  by  bringing 

them  within  easy  comprehension  to  increase  his  interest  in  the  study 

of  the  subject. 

Gibbes'  Practical  Histology  and  Pathology.  Third  Edition. 
Enlarged.  i2mo.  Cloth,  1.75 

Virchow's  Post-Mortem  Examinations.    2d  Ed.    Cloth,  i.oo 


PHYSIOLOGY. 


Yeo's 
dents 


's  Physiology.  Fourth  Edition.  The  most  Popular  Stu- 
nts' Book.  By  Gerald  F.  Yeo,  M.D.,  F.R.C.S.,  Professor  of 
Physiology  in  King's  College,  London.  Small  Octavo.  758 
pages.  321  carefully  printed  Illustrations.  With  a  Full 
Glossary  and  Index.  See  Page  3.  Cloth,  3.00;  Leather,  3.50 

Brubaker's  Compend  of  Physiology.  Illustrated.  Fifth 
Edition.  Cloth,  i.oo;  Interleaved  for  Notes,  1.25 

Stirling.  Practical  Physiology,  including  Chemical  and  Ex- 
perimental Physiology.  142  Illustrations.  Cloth,  2.25 

Kirke's  Physiology.  New  i2th  Ed.  Thoroughly  Revised  and 
Enlarged.  502  Illustrations.  Cloth,  4.00;  Leather,  5.00 

Landois'  Human  Physiology.  Including  Histology  and  Micro- 
scopical Anatomy,  and  with  special  reference  to  Practical  Medi- 
cine. Third  Edition.  Translated  and  Edited  by  Prof.  Stirling. 
692  Illustrations.  Cloth,  6.50;  Leather,  7.50 

"  With  this  Text-book  at  his  command,  no  student  could  fail  in 

his  examination."  —  Lancet. 

Sanderson's  Physiological  Laboratory.  Being  Practical  Ex- 
ercises for  the  Student.  350  Illustrations.  8vo.  Cloth,  5.00 

Tyson's  Cell  Doctrine.  Its  History  and  Present  State.  Illus- 
trated. Second  Edition.  Cloth,  2.00 

Hff-  Set  pages  14  and  15  for  list  of  'Quiz-Commends  f 


12        STUDENTS'  TEXT-BOOKS  AND  MANUALS. 

PRACTICE. 

Taylor.  Practice  of  Medicine.  A  Manual.  By  Frederick 
Taylor,  M.D.,  Physician  to,  and  Lecturer  on  Medicine  at,  Guy's 
Hospital,  London;  Physician  to  Evelina  Hospital  for  Sick  Chil- 
dren, and  Examiner  in  Materia  Medica  and  Pharmaceutical 
Chemistry,  University  of  London.  Cloth,  4.00 

Roberts'  Practice.  New  Revised  Edition.  A  Handbook 
of  the  Theory  and  Practice  of  Medicine.  By  Frederick  T. 
Roberts,  M.D.  ;  M.R.C.P.,  Professor  of  Clinical  Medicine  and 
Therapeutics  in  University  College  Hospital,  London.  Seventh 
Edition.  Octavo.  Cloth,  5.50  ;  Sheep,  6.50 

Hughes.  Compend  of  the  Practice  of  Medicine.  4th  Edi- 
tion. Two  parts,  each,  Cloth,  i.oo;  Interleaved  for  Notes,  1.25 
PART  i. — Continued,  Eruptive  and  Periodical  Fevers,  Diseases 

of  the  Stomach,  Intestines,   Peritoneum,  Biliary  Passages,  Liver, 

Kidneys,  etc.,  and  General  Diseases,  etc. 

PART   n. — Diseases   of   the   Respiratory    System,   Circulatory 

System  and  Nervous  System ;  Diseases  of  the  Blood,  etc. 
Physician's  Edition.    Fourth  Edition.    Including  a  Section 
on  Skin  Diseases.   With  Index,    i  vol.  Full  Morocco,  Gilt,  2.50 

Tanner's  Index  of  Diseases,  and  Their  Treatment.    Cloth,  3.00 

PRESCRIPTION   BOOKS. 

Wythe's  Dose  and  Symptom  Book.  Containing  the  Doses 
and  Uses  of  all  the  principal  Articles  of  the  Materia  Medica,  etc. 
Seventeenth  Edition.  Completely  Revised  and  Rewritten.  Just 
Ready.  321110.  Cloth,  i.oo;  Pocket-book  style,  1.25 

Pereira's  Physician's  Prescription  Book.  Containing  Lists 
of  Terms,  Phrases,  Contractions  and  Abbreviations  used  in 
Prescriptions  Explanatory  Notes,  Grammatical  Construction  of 
Prescriptions,  etc..,  etc.  By  Professor  Jonathan  Pereira,  M.D. 
Sixteenth  Edition.  32mo.  Cloth,  i.oo;  Pocket-book  style,  1.25 

PHARMACY. 

Stewart's  Compend  of  Pharmacy.  Based  upon  Remington's 
Text-Book  of  Pharmacy.  Second  Edition,  Revised. 

Cloth,  i.oo  ;  Interleaved  for  Notes,  1.25 

SKIN  DISEASES. 

Anderson,  (McCall)  Skin  Diseases.  A  complete  Text-Book, 
with  Colored  Plates  and  numerous  Wood  Engravings.  8vo. 
Just  Ready.  Cloth,  4.50;  Leather,  5.50 

Van  Harlingen  on  Skin  Diseases.  A  Handbook  of  the  Dis- 
eases of  the  Skin,  their  Diagnosis  and  Treatment  (arranged  alpha- 
betically). By  Arthur  Van  Harlingen,  M.D.,  Clinical  Lecturer 
on  Dermatology,  Jefferson  Medical  College ;  Prof,  of  Diseases  of 
the  Skin  in  the  Philadelphia  Polyclinic.  2d  Edition.  Enlarged. 
With  colored  and  other  plates  and  illustrations.  12010.  Cloth,  2.50 

Bulkley.  The  Skin  in  Health  and  Disease.  By  L.  Duncan 
Bulkley,  Physician  to  the  N.  Y.  Hospital.  Illus.  Cloth,  .50 

JKS~  See  pages  2  to  3  for  list  of  New  Manuals. 


STUDENTS'  TEXT-BOOKS  AND  MANUALS.        13 

SURGERY. 

Caird  and  Cathcart.  Surgical  Handbook  for  the  use  of 
Practitioners  and  Students.  By  F.  MITCHELL  CAIRO,  M  B., 
F.R.C.S.,  and  C.  WALKER  CATHCART,  M.B.,  F.R.C.S.,  Asst.  Sur- 
geons Royal  Infirmary.  With  over  200  Illustrations.  400  pages. 
Pocket  size.  Leather  covers,  2.50 

Jacobson.  Operations  in  Surgery.  A  Systematic  Handbook 
for  Physicians,  Students  and  Hospital  Surgeons.  By  W.  H.  A. 
Jacobson,  B.A.,  Oxon.  F.R.C.S.  Eng. ;  Ass't  Surgeon  Guy's  Hos- 
pital ;  Surgeon  at  Royal  Hospital  for  Children  and  Women,  etc. 
199  Illustrations.  1006  pages.  8vo.  Cloth.  5.00;  Leather,  6.00 

Heath's  Minor  Surgery,  and  Bandaging.  Ninth  Edition.  142 
Illustrations.  60  Formulae  and  Diet  Lists.  Cloth,  2.00 

Horwitz's  Compend  of  Surgery,  including  Minor  Surgery, 
Amputations,  Fractures,  Dislocations,  Surgical  Diseases,  and  the 
Latest  Antiseptic  Rules,  etc.,  with  Differential  Diagnosis  and 
Treatment.  By  ORVILLE  HORWITZ,  B.S.,  M.D.,  Demonstrator  of 
Surgery,  Jefferson  Medical  College.  3d  edition.  Enlarged  and 
Rearranged.  91  Illustrations  and  77  Formulae.  12010. 

Cloth,  i. oo ;  Interleaved  for  the  addition  of  Notes,  1.25 

Walsham.  Manual  of  Practical  Surgery.  For  Students  and 
Physicians.  By  WM.  J.  WALSHAM,  M.D.,  F.R.C.S.,  Asst.  Surg. 
to,  and  Dem.  of  Practical  Surg.  in,  St.  Bartholomew's  Hospital, 
Surgeon  to  Metropolitan  Free  Hospital,  London.  With  236 
Engravings.  See  Page  2.  Cloth,  3.00;  Leather,  3.50 

URINE,  URINARY   ORGANS,  ETC. 

Acton.  The  Reproductive  Organs.  In  Childhood,  Youth, 
Adult  Life  and  Old  Age.  Seventh  Edition.  Cloth,  2.00 

Beale.  Urinary  and  Renal  Diseases  and  Calculous  Disorders. 
Hints  on  Diagnosis  and  Treatment.  i2mo.  Cloth,  1.75 

Holland.  The  Urine,  and  Common  Poisons  and  The 
Milk.  Chemical  and  Microscopical,  for  Laboratory  Use.  Illus- 
trated. Third  Edition.  i2mo.  Interleaved.  Cloth,  i.oo 

Ralfe.  Kidney  Diseases  and  Urinary  Derangements.  42  Illus- 
trations. i2mo.  572  pages.  Cloth,  2.75 

Legg.     On  the  Urine.    A  Practical  Guide.     6th  Ed.    Cloth,  .75 

Marshall  and  Smith.  On  the  Urine.  The  Chemical  Analysis  of 
the  Urine.  By  John  Marshall,  M.D.,  Chemical  Laboratory,  Univ. 
of  Penna;  and  Prof.  E.  F.  Smith,  PH.D.  Col.  Plates.  Cloth,  i.oo 

Thompson.  Diseases  of  the  Urinary  Organs.  Eighth 
London  Edition.  Illustrated.  Cloth,  3.50 

Tyson.  On  the  Urine.  A  Practical  Guide  to  the  Examination 
of  Urine.  With  Colored  Plates  and  W6od  Engravings.  6th  Ed. 
Enlarged.  lamo.  Cloth,  1.50 

Bright's  Disease  and  Diabetes.    Illus.          Cloth,  3.50 

Van  Niiys,  Urine  Analysis.    Illus.  Cloth,  a.oo 

VENEREAL  DISEASES. 

Hill  and  Cooper.  Student's  Manual  of  Venereal  Diseases, 
with  Formulae.  Fourth  Edition.  i2mo.  Cloth,  i.oo 

Durkee.    On   Gonorrhoea  and   Syphilis.    Illus.      Cloth,  3.50 
4S-  See  pages  14  and  13  for  list  of  ?  Quiz-Compends .' 


NEW  AND  REVISED  EDITIONS. 

PQUIZ-COMPENDS? 

The  Best  Compends  for  Students'  Use 
in  the  Quiz  Class,  and  when  Pre- 
paring for  Examinations. 

Compiled  in  accordance  with  the  latest  teachings  of  promi- 
nent lecturers  and  the  most  popular  Text-books. 

They  form  a  most  complete,  practical  and  exhaustive 
set  of  manuals,  containing  information  nowhere  else  col- 
lected in  such  a  condensed,  practical  shape.  Thoroughly 
np  to  the  times  in  every  respect,  containing  many  new 
prescriptions  and  formulae,  and  over  two  hundred  and 
fifty  illustrations,  many  of  which  have  been  drawn  and 
engraved  specially  for  this  series.  The  authors  have  had 
large  experience  as  quiz-masters  and  attaches  of  colleges, 
with  exceptional  opportunities  for  noting  the  most  recent 
advances  and  methods. 

Cloth,  each  $1.00.     Interleaved  for  Notes,  $1.25. 
No.  i.  HUMAN  ANATOMY,  "Based upon  Gray."  Fourth 
Edition,  including  Visceral  Anatomy,  formerly  published 
separately.     Over  100  Illustrations.      By  SAMUEL  O.  L. 
POTTER,  M.A.,  M.D.,  late  A.  A.  Surgeon  U.  S.  Army.     Professor 
of  Practice,  Cooper  Medical  College,  San  Francisco. 
Nos.  2  and  3.     PRACTICE  OF  MEDICINE.    Fourth  Edi- 
tion.    By  DANIEL  E.  HUGHES,  M.D.,  Demonstrator  of  Clinical 
Medicine  in  Jefferson  Medical  College,  Philadelphia.  In  two  parts. 
PART  I. — Continued,  Eruptive  and  Periodical  Fevers,  Diseases 
of  the  Stomach,  Intestines,  Peritoneum,  Biliary  Passages,  Liver, 
Kidneys,  etc.  (including  Tests  for  Urine),  General  Diseases,  etc. 

PART  II. — Diseases  of  the  Respiratory  System  (including  Phy- 
sical Diagnosis),  Circulatory  System  and  Nervous  System;  Dis- 
eases of  the  Blood,  etc. 

***  These  little  books  can  be  regarded  as  a  full  set  of  notes  upon 
the  Practice  of  Medicine,  containing  the  Synonyms,  Definitions, 
Causes,  Symptoms,  Prognosis,  Diagnosis,  Treatment,  etc.,  of  each 
disease,  and  including  a  number  of  prescriptions  hitherto  unpub- 
lished. 

No.  4.  PHYSIOLOGY,  including  Embryology.  Fifth 
Edition.  By  ALBERT  P.  BRUBAKER,  M.D.,  Prof,  of  Physiology, 
Penn'a  College  of  Dental  Surgery  ;  Demonstrator  of  Physiology 
in  Jefferson  Medical  College,  Philadelphia.  Revised,  Enlarged 
and  Illustrated. 

No.  5.  OBSTETRICS.  Illustrated.  Fourth  Edition.  By 
HENRY  G.  LANDIS,  M.D.,  Prof,  of  Obstetrics  and  Diseases  of 
Women,  in  Starling  Medical  College,  Columbus,  O.  Revised 
Edition.  New  Illustrations. 


BLAKISTON'S  ?  QUIZ-COMPENDS  ? 

Continued. 
Bound  in  Cloth,  $1.00.  Interleaved,  for  Notes,  $1.25 

No.  6.  MATERIA  MEDICA,  THERAPEUTICS  AND 
PRESCRIPTION  WRITING.  Fifth  Revised  Edition. 
With  especial  Reference  to  the  Physiological  Action  of  Drugs, 
and  a  complete  article  on  Prescription  Writing.  Based  on  the 
Last  Revision  of  the  U.  S.  Pharmacopoeia,  and  including  many 
unofficinal  remedies.  By  SAMUEL  O.  L.  POTTER,  M.A.,  M.D., 
late  A.  A.  Surg.  U.  S.  Army;  Prof,  of  Practice,  Cooper  Medical 
College,  San  Francisco.  Improved  and  Enlarged,  with  Index. 

No.  7.  GYNAECOLOGY.  A  Compend  of  Diseases  of  Women. 
By  HENRY  MORRIS,  M.D.,  Demonstrator  of  Obstetrics,  Jefferson 
Medical  College,  Philadelphia. 

No.  8.    DISEASES  OF  THE  EYE  AND  REFRACTION, 

including  Treatment  and  Surgery.  By  L.  WEBSTER  Fox,  M.D., 
Chief  Clinical  Assistant  Ophthalmological  Dept.,  Jefferson  Med- 
ical College,  etc.,  and  GEO.  M.  GOULD,  M.D.  71  Illustrations,  39 
Formulae.  Second  Enlarged  and  improved  Edition.  Index. 

No.  9.  SURGERY.  Illustrated.  Third  Edition.  Including 
Fractures,  Wounds,  Dislocations,  Sprains,  Amputations  and 
other  operations;  Inflammation,  Suppuration,  Ulcers,  Syphilis, 
Tumors,  Shock,  etc.  Diseases  of  the  Spine,  Ear,  Bladder,  Tes- 
ticles, Anus,  and  other  Surgical  Diseases.  By  ORVILLH  HORWITZ, 
A.M.,  M.D.,  Demonstrator  of  Surgery,  Jefferson  Medical  Col- 
lege. Revised  and  Enlarged.  77  Formulas  and  91  Illustrations. 

No.  10.  CHEMISTRY.  Inorganic  and  Organic.  For  Medical 
and  Dental  Students.  Including  Urinary  Analysis  and  Medical 
Chemistry.  By  HENRY  LEFFMANN,  M.D.,  Prof,  of  Chemistry  in 
Penn'a  College  of  Dental  Surgery,  Phila.  Third  Edition,  Revised 
and  Rewritten,  with  Index. 

No.  u.  PHARMACY.  Based  upon  "  Remington's  Text-book 
of  Pharmacy."  By  F.  E.  STEWART,  M.D.,  PH.G.,  Quiz-Master 
at  Philadelphia  College  of  Pharmacy.  Second  Edition,  Revised. 

No.  12.  VETERINARY  ANATOMY  AND  PHYSIOL- 
OGY. 29  Illustrations.  By  WM.  R.  BALLOU,  M.D.,  Prof,  of 
Equine  Anatomy  at  N.  Y.  College  of  Veterinary  Surgeons. 

No.  13.  DISEASES  OF  CHILDREN.  By  DR.  MARCUS  P. 
HATFIELD,  Prof,  of  Diseases  of  Children,  Chicago  Medical 
College. 

Bound  in  Cloth,  $1.    Interleaved,  for  the  Addition  of  Notes,  $1.25. 


These  books  are  constantly  revised  to  keep  up  with 
the  latest  teachings  and  discoveries,  so  that  they  contain 
all  the  new  methods  and  principles.  No  series  of  books 
are  so  complete  in  detail,  concise  in  language,  or  so  well 
printed  and  bound.  Each  one  forms  a  complete  set  of 
notes  upon  the  subject  under  consideration. 

Descriptive  Circular  Free. 


NOW  READY. 


A  NEW 

MEDICAL 

DICTIONARY 

BY  GEORGE  M.  GOULD, 

Ophthalmic  Surgeon,  Philadelphia  Hospital,  etc. 


AN  ENTIRELY  NEW  BOOK. 
BASED  ON  RECENT  MEDICAL  LITERATURE. 

Small  Octavo.    520  Pages.     Handsomely  Printed. 

Bound  in  Half  Dark  Leather,  $3.25. 

Half  Morocco,  Thumb  Index,  $4.25. 


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STAMPED  BELOW 

Books  not  returned  on  time  are  subject  to  a  fine  of 
50c  per  volume  after  the  third  day  overdue,  increasing 
to  $1.00  per  volume  after  the  sixth  day.  Books  not  in 
demand  may  be  renewed  if  application  is  made  before 
expiration  of  loan  period. 


HOV  26  192 


YB  66668 


1 


